Add metrics for source branch exceptions for approval policy

What does this MR do and why?

This MR adds metrics for security policy with source branch exceptions through bypass_settings

Local testing output

Key Path	Monitored Events	Instrumentation Class	Initial Value	Current Value
redis_hll_counters.count_distinct_project_id_from_check_branch_exceptions_bypass_settings_for_approval_policy_monthly	check_branch_exceptions_bypass_settings_for_approval_policy	UniqueCountMetric	1	1
redis_hll_counters.count_distinct_project_id_from_check_branch_exceptions_bypass_settings_for_approval_policy_weekly	check_branch_exceptions_bypass_settings_for_approval_policy	UniqueCountMetric	1	1

References

• #549575 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Create a group or a project
• Create MR approval policy with branch exceptions:

approval_policy:
  - name: Branch Bypass
    description: ''
    enabled: true
    rules:
      - type: any_merge_request
        branch_type: protected
        commits: any
    actions:
      - type: require_approval
        approvals_required: 1
        role_approvers:
          - maintainer
          - developer
      - type: send_bot_message
        enabled: true
    approval_settings:
      block_branch_modification: true
      prevent_pushing_and_force_pushing: true
      prevent_approval_by_author: true
      prevent_approval_by_commit_author: true
      remove_approvals_with_new_commit: true
      require_password_to_approve: false
    fallback_behavior:
      fail: closed
    bypass_settings:
      branches:
        - source:
            pattern: hotfix*
          target:
            name: main

• Before merging the MR to update the policy, listen for the events:

bundle exec rails runner scripts/internal_events/monitor.rb check_branch_exceptions_bypass_settings_for_approval_policy

• Merge the MR and verify that the metric is updated

MR acceptance checklist

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