Parse error for source and outline problem area

What does this MR do and why?

Parse error for source and outline problem area

• parse error from backend
• show validation state for scan execution action variables
• show validation state for merge request approval rule scan type
• sets up framework to add validation states for any other components

Changelog: added

EE: true

MR acceptance checklist

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Screenshots or screen recordings

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Upload a GitLab Ultimate license
2. Navigate to a project => Secure => Policies => New policy => Scan execution
3. Add a new criteria and try to save the policy without selecting the value
4. Verify the alert appears and the correct variables inputs are outlined in red

Related to #419406 (closed)