Include coverage reports from child pipeline

What does this MR do and why?

Include coverage reports from child pipelines when creating pipeline coverage report.

Part of #363301 (closed).

Screenshots or screen recordings

In this sample MR, alberts-gitlab/test-ruby-cobertura!2, there is a parent and child pipeline set up to generate coverage. The parent pipeline generates coverage for demo.rb. The child pipeline generates coverage for demo_child.rb.

Before - coverage from child pipeline is not included:

After - coverage from child pipeline is included:

Example project and MR: alberts-gitlab/test-ruby-cobertura!2

How to set up and validate locally

1. Clone project https://gitlab.com/alberts-gitlab/test-ruby-cobertura locally
2. Pull branch https://gitlab.com/alberts-gitlab/test-ruby-cobertura/-/tree/test-coverage-child-pipeline containing CI and test changes to generate coverage from child pipeline.
3. Create MR in GDK and wait for pipeline to succeed.
4. Verify that the demo_child.rb coverage generated in the child pipeline is not shown in the MR diff.
5. Enable feature flag ci_child_pipeline_coverage_reports.

   Feature.enable(:ci_child_pipeline_coverage_reports)

6. Run a new pipeline on the branch and wait for it to succeed.
7. Verify that the demo_child.rb coverage is now shown in the MR diff.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

doc/install/aws/gitlab_hybrid_on_aws.md

@@ -168,7 +168,7 @@ If EKS node autoscaling is employed, it is likely that your average loading will
 | Gitaly Instances (in ASG)                                    | 12 vCPU, 45GB<br />(across 3 nodes)                          | **m5.xlarge** x 3 nodes<br />(48 vCPU, 180 GB)          | $0.192 x 3 = $0.58/hr           | $0.192 x 3 = $0.58/hr           |
 |                                                              | The GitLab Reference architecture for 2K is not Highly Available and therefore has a single Gitaly no Praefect. AWS Quick Starts MUST be HA, so it implements Prafect from the 3K Ref Architecture to meet that requirement |                                                         |                                 |                                 |
 | Praefect (Instances in ASG with load balancer)               | 6 vCPU, 10 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | **c5.large** x 3 nodes<br />(6 vCPU, 12 GB)             | $0.09 x 3 = $0.21/hr            | $0.09 x 3 = $0.21/hr            |
-| Praefect PostgreSQL(1) (AWS RDS)                             | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | Not applicable; Reuses GitLab PostgreSQL                            | $0                              | $0                              |
+| Praefect PostgreSQL(1) (AWS RDS)                             | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | Not applicable; reuses GitLab PostgreSQL                            | $0                              | $0                              |
 | Internal Load Balancing Node                                 | 2 vCPU, 1.8 GB                                               | AWS ELB                                                 | $0.10/hr                        | $0.10/hr                        |
 
 ### 3K Cloud Native Hybrid on EKS
@@ -222,7 +222,7 @@ If EKS node autoscaling is employed, it is likely that your average loading will
 | **<u>Gitaly Cluster</u>** [Details](gitlab_sre_for_aws.md#gitaly-sre-considerations) |                                                              |                                                         |                                 |                                                              |
 | Gitaly Instances (in ASG)                                    | 12 vCPU, 45GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | **m5.large** x 3 nodes<br />(12 vCPU, 48 GB)            | $0.192 x 3 = $0.58/hr           | [Gitaly & Praefect Must Have an Uneven Node Count for HA](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) |
 | Praefect (Instances in ASG with load balancer)               | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | **c5.large** x 3 nodes<br />(6 vCPU, 12 GB)             | $0.09 x 3 = $0.21/hr            | [Gitaly & Praefect Must Have an Uneven Node Count for HA](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) |
-| Praefect PostgreSQL(1) (Amazon RDS)                             | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | Not applicable; Reuses GitLab PostgreSQL                            | $0                              |                                                              |
+| Praefect PostgreSQL(1) (Amazon RDS)                             | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | Not applicable; reuses GitLab PostgreSQL                            | $0                              |                                                              |
 | Internal Load Balancing Node                                 | 2 vCPU, 1.8 GB                                               | AWS ELB                                                 | $0.10/hr                        | $0.10/hr                                                     |
 
 ### 5K Cloud Native Hybrid on EKS
@@ -276,7 +276,7 @@ If EKS node autoscaling is employed, it is likely that your average loading will
 | **<u>Gitaly Cluster</u>** [Details](gitlab_sre_for_aws.md#gitaly-sre-considerations) |                                                              |                                                         |                                 |                                                              |
 | Gitaly Instances (in ASG)                                    | 24 vCPU, 90GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | **m5.2xlarge** x 3 nodes<br />(24 vCPU, 96GB)           | $0.384 x 3 = $1.15/hr           | [Gitaly & Praefect Must Have an Uneven Node Count for HA](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) |
 | Praefect (Instances in ASG with load balancer)               | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | **c5.large** x 3 nodes<br />(6 vCPU, 12 GB)             | $0.09 x 3 = $0.21/hr            | [Gitaly & Praefect Must Have an Uneven Node Count for HA](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) |
-| Praefect PostgreSQL(1) (Amazon RDS)                             | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | Not applicable; Reuses GitLab PostgreSQL                            | $0                              |                                                              |
+| Praefect PostgreSQL(1) (Amazon RDS)                             | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | Not applicable; reuses GitLab PostgreSQL                            | $0                              |                                                              |
 | Internal Load Balancing Node                                 | 2 vCPU, 1.8 GB                                               | AWS ELB                                                 | $0.10/hr                        | $0.10/hr                                                     |
 
 ### 10K Cloud Native Hybrid on EKS
@@ -329,7 +329,7 @@ If EKS node autoscaling is employed, it is likely that your average loading will
 | **<u>Gitaly Cluster</u>** [Details](gitlab_sre_for_aws.md#gitaly-sre-considerations) |  |  |  |  |
 | Gitaly Instances (in ASG) | 48 vCPU, 180GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | **m5.4xlarge** x 3 nodes<br />(48 vCPU, 180 GB) | $0.77 x 3 = $2.31/hr | [Gitaly & Praefect Must Have an Uneven Node Count for HA](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) |
 | Praefect (Instances in ASG with load balancer) | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | **c5.large** x 3 nodes<br />(6 vCPU, 12 GB) | $0.09 x 3 = $0.21/hr | [Gitaly & Praefect Must Have an Uneven Node Count for HA](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) |
-| Praefect PostgreSQL(1) (Amazon RDS) | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | Not applicable; Reuses GitLab PostgreSQL | $0 |  |
+| Praefect PostgreSQL(1) (Amazon RDS) | 6 vCPU, 5.4 GB<br />([across 3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections)) | Not applicable; reuses GitLab PostgreSQL | $0 |  |
 | Internal Load Balancing Node | 2 vCPU, 1.8 GB | AWS ELB | $0.10/hr | $0.10/hr |
 
 ### 50K Cloud Native Hybrid on EKS
@@ -382,7 +382,7 @@ If EKS node autoscaling is employed, it is likely that your average loading will
 | **<u>Gitaly Cluster</u>** [Details](gitlab_sre_for_aws.md#gitaly-sre-considerations) |                                                              |                                                           |                                 |                                                              |
 | Gitaly Instances (in ASG)                                    | 64 vCPU, 240GB x [3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) | **m5.16xlarge** x 3 nodes<br />(64 vCPU, 256 GB each)     | $3.07 x 3 = $9.21/hr            | [Gitaly & Praefect Must Have an Uneven Node Count for HA](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) |
 | Praefect (Instances in ASG with load balancer)               | 4 vCPU, 3.6 GB x [3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) | **c5.xlarge** x 3 nodes<br />(4 vCPU, 8 GB each)          | $0.17 x 3 = $0.51/hr            | [Gitaly & Praefect Must Have an Uneven Node Count for HA](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) |
-| Praefect PostgreSQL(1) (AWS RDS)                             | 2 vCPU, 1.8 GB x [3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) | Not applicable; Reuses GitLab PostgreSQL                              | $0                              |                                                              |
+| Praefect PostgreSQL(1) (AWS RDS)                             | 2 vCPU, 1.8 GB x [3 nodes](gitlab_sre_for_aws.md#gitaly-and-praefect-elections) | Not applicable; reuses GitLab PostgreSQL                              | $0                              |                                                              |
 | Internal Load Balancing Node                                 | 2 vCPU, 1.8 GB                                               | AWS ELB                                                   | $0.10/hr                        | $0.10/hr                                                     |
 
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