FE: Show warning when approval settings are overridden for MR

What does this MR do and why?

Show warning when approval settings are overridden for MR

• Add a warning icon in ApprovalsSummary based on the data
• Handle potentially missing data and show generic popover text

GraphQL type is added in !175614 (merged). We have to wait until BE is deployed to production before we can merge this one.

References

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• BE changes: !175614 (merged)

MR acceptance checklist

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Generic / when policy details are not populated	With single policy	With multiple policies

How to set up and validate locally

1. Create a project
2. In the project, create a policy which overrides approval settings:

   approval_policy:
     - name: Any commit approvals
       description: ''
       enabled: false
       rules:
         - type: any_merge_request
           branch_type: protected
           commits: any
       actions:
         - type: require_approval
           approvals_required: 1
           role_approvers:
             - 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: false
         require_password_to_approve: false
       fallback_behavior:
         fail: closed
   

3. Create MR and verify there's a warning icon in the MR widget and the link in the popover goes to the policy edit page
4. Add another policy
5. Verify that both policies show up
6. Remove the approval_settings block from the YAML and verify that there's no warning
7. Update the violations to remove the link to Security::ApprovalPolicyRule

   MergeRequest.last.scan_result_policy_violations.update_all(approval_policy_rule_id: nil)

8. Verify that a generic popover is shown without listing the policy details

Related to #478175 (closed)