Resolve "List Gitaly calls and arguments in the performance bar"

What does this MR do?

Add Gitaly details to the performance bar.

Are there points in the code the reviewer needs to double check?

Yep!

1. The way of getting the Gitaly request details is kind of sketchy.
2. There's not a super-clear separation at the moment between whether values should be formatted in the performance bar class, the place where they're generated, or even in the JS that inserts these.
3. Specs? There aren't any at the moment.

Why was this MR needed?

It's hard to see where we spend our time in Gitaly, at the moment.

Screenshots (if relevant)

What are the relevant issue numbers?

Closes #43805 (closed).