E2E: Validate merge request comments are migrated

What does this MR do and why?

Describe in detail what your merge request does and why.

• Moves project migration spec back from EE
• Adds mr comment validation to mr migration spec
• Fixes issue with eventually_matcher call without explicit args
• Improves failure output for eventually_matcher

Next iteration:

• Refactor mr setup to use api instead of Repository::ProjectPush which is very slow

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Closes: #348544 (closed)