Migrate revision dropdown to use GlCollapsibleListbox

What does this MR do and why?

As part of the effort to deprecate old dropdown components, this MR refactors to use GlCollapsibleListbox for the revision dropdown.

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• #450557 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

	Before	After
Search for branch/tag
Search for commit	CleanShot 2025-03-25 at 15.02.25.mp4	CleanShot 2025-03-25 at 14.43.06.mp4

How to set up and validate locally

1. Visit a project/directory under a project
2. Select another branch/tag
   1. For searching commit, enter the commit sha and press enter
3. Select compare
4. Both revision dropdown should work as before:
   1. Try searching
   2. Try selecting

Thank you

the one and only @pgascouvaillancourt for the awesome pairing 🍐

Related to #450557 (closed)