FE: Create schedule agent rule component

Why are we doing this work

• Users want to create rules that are based off of a schedule for a cluster

Relevant links

NOTE: Instead of cluster, use agent

Namespace Labels

Non-functional requirements

• Feature flag:
• Testing:

Implementation plan

• frontend create schedule agent rule mode on both the project and group levels (for more context, read the schedule schema docs)
  • look at scan_result_policy_editor.vue for examples on using the policy_rule_builder.vue component
  • rule dropdown
    • there are two options for rules:
      1. A pipeline is run (handled by FE: Create pipeline rule component (#359885 - closed))
      2. Schedule (handled by this issue)
    • for this issue, only focus on 2, but feel free to make it a drop down
  • agents dropdown
    • per &5363 (comment 894764465), give the user an input box instead for the user to type comma-delimited agents for MVP. There is a graphql endpoint for both (e.g. Project.clusterAgents and Group.clusterAgents), so this could be a dropdown for v2
  • namespace dropdown
    • per #365820 (comment 998547239), give the user an input box instead for the user to type comma-delimited namespaces because there is no endpoint to retrieve all namespaces
  • CRON dropdowns
    • per &5363 (comment 894814030), limit users to only specific schedules, allowing a user to use yaml mode to do anything more complicated

Verification steps

1. Upload a GitLab Ultimate license
2. Turn on the :scan_execution_rule_mode feature flag
3. Navigate to a project => Security & Compliance => Policies => New policy => Scan Execution Policy
4. Verify rule mode schedule agent rule works
5. Navigate to a group => Security & Compliance => Policies => New policy => Scan Execution Policy
6. Verify rule mode schedule agent rule works