Add summary for schedule pipeline policy

What does this MR do and why?

Add summary for schedule pipeline policy

• generate summary if a schedule exists
• create sentence structure for summary
• pipeline_execution_schedule_policy policies cannot be retrieved from the backend yet, so this code relies on mocking the response
• create tests

EE: true

References

Screenshots or screen recordings

Example summaries

How to set up and validate locally

1. Upload a GitLab Ultimate license
2. Navigate to a project/group => Secure => Policies => New policy => Pipeline execution policy => Create a new policy
3. Add the following patch

diff --git a/ee/app/assets/javascripts/security_orchestration/components/policy_drawer/pipeline_execution/details_drawer.vue b/ee/app/assets/javascripts/security_orchestration/components/policy_drawer/pipeline_execution/details_drawer.vue
index c3efd4648c37..223364ce1f39 100644
--- a/ee/app/assets/javascripts/security_orchestration/components/policy_drawer/pipeline_execution/details_drawer.vue
+++ b/ee/app/assets/javascripts/security_orchestration/components/policy_drawer/pipeline_execution/details_drawer.vue
@@ -51,8 +51,30 @@ export default {
       return this.policy?.policyScope;
     },
     parsedYaml() {
+      // TODO remove
+      const mockPipelineExecutionSchedulePolicy = `name: ''
+description: ''
+enabled: true
+content:
+  include:
+    - project: gitlab-org/gitlab-test
+      file: .gitlab-ci.yml
+skip_ci:
+  allowed: false
+schedules:
+  - branch_type: protected
+    type: weekly
+    start_time: '00:00'
+    time_window:
+      value: 86400
+      distribution: random
+    timezone: Pacific/Midway
+    days:
+      - monday
+      - thursday`;
       return fromYaml({
-        manifest: this.policy.yaml,
+        manifest: mockPipelineExecutionSchedulePolicy,
+        // manifest: this.policy.yaml,
         type: POLICY_TYPE_COMPONENT_OPTIONS.pipelineExecution.urlParameter,
       });
     },

4. Navigate to a project/group => Secure => Policies => Select the pipeline execution policy
5. Verify the summary drawer

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #505174 (closed)