Bypass markdown for commit titles on MR notes

This MR avoids commit titles being evaluated by GFM by using actual ul and li tags on SystemNoteService to build the commits information. Markdown isn't evaluated inside HTML block tags.

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/37616