RFE: Sticky scroll toolbar on merge request review

Proposal

When reviewing a merge request, you generally want to review it commit-by-commit to get the most understandable context. I.e., you open diffs via the "Commits" tab.

In this mode, you have toolbar with some useful buttons to make it easier to navigate the set of commits:

The file browser toggle is very useful if you have limited space to switch between word wrapping and moving around a large commit. The Prev/Next buttons are convenient to quickly switch commits in case you need to jump around to get a good understanding.

Unfortunately, this toolbar stays at the top and becomes inaccessible once you scroll down. This unfortunately severely decreases its usefulness, as you now have to scroll back up, click the file browser toggle, scroll back down.

I propose to make it sticky scroll, just like the tabs above it. That would make it easily accesible wherever you are in the commit.

(There is also #336273, which seems to have a partial overlap with this proposal.)