Make version and target drop downs more obvious

[daveverwer]

Discussed in #2177

^{Originally posted by finestructure December 6, 2022}
I feel like we've discussed this before somewhere but couldn't find any issues or discussions.

In a recent PR, someone commented:

it takes you to the Instrumentation documentation instead of Tracing without any UI to switch to the Tracing documentation

I actually initially overlooked this comment and then while helping with the PR ended up struggling to figure out if my fix worked, because I couldn't find the target picker 🙈

So I think there's something there that may need addressing.

It may be as simple as adding a drop-down chevron to indicate the breadcrumb is a menu here:

(and to the version segment as well while we're at it).

[daveverwer]

Original discussion in #2022