Show various MR keyboard shorcuts in tooltips

What does this MR do and why?

Show various MR keyboard shortcuts in tooltips:

• Next/previous commit
• Next/previous unresolved thread

Additionally:

1. Improves display of toggle file browser keyboard shortcut
2. Renames the unresolved thread keyboard shortcuts to use “thread” instead of “discussion”

Changelog: changed

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.

Shortcuts	Before	After
Enabled		CleanShot 20240129153007.mp4
Disabled		CleanShot 20240129152759.mp4

How to set up and validate locally

Do these steps with keyboard shortcuts enabled and disabled:

1. Visit a merge request with more than one commit.
2. If no unresolved threads exist, create a thread.
3. Go to “Commits” tab and click on a commit.
4. Hover/focus these buttons:
   1. Toggle file browser
   2. Next/previous commit
   3. Next/previous unresolved thread