Add QA test for actions on prometheus alerts

What does this MR do?

Reopens !20591 (merged) to adds a QA test for managing alert rules through the GitLab UI, but with some necessary EE fixes.

Related Issue: #198420 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers