Add feature flags for moving reports to the backend

Problem to solve

We need to put the work we're doing in &1425 (closed) behind a series of feature flags. It makes sense to split the creation of these flags into a separate issue so we can work more effectively.

Further details

We should follow this naming convention of, [report_type][report_location]ReportApi. For example, the SAST MR reports will be behind the feature flag, sastMergeRequestReportApi.

It turns out we should be able to switch all of the pipelines view's report types over to the backend logic in one go, so can use just a single feature flag for it instead.

Proposal

Create the following feature flags, make them off by default and available to the frontend.

• sastPipelineReportApi

• dastPipelineReportApi

• containerScanningPipelineReportApi

• dependencyScanningPipelineReportApi

• licenceManagementPipelineReportApi licenseManagementPipelineReportApi *⃣

• pipelineReportApi

• sastMergeRequestReportApi

• dastMergeRequestReportApi

• containerScanningMergeRequestReportApi

• dependencyScanningMergeRequestReportApi

• licenceManagementMergeRequestReportApi licenseManagementMergeRequestReportApi *⃣

*⃣ Code should be written in US English.

Testing

This is a ~backstage change and will not need testing. But be sure to test that the flags are available on the required pages.

Links / references

https://docs.gitlab.com/ee/user/project/operations/feature_flags.html

https://docs.gitlab.com/ee/development/feature_flags/development.html