This PR introduces a project dropdown when working with multiple
folders/projects in one workspace. Here are some interaction details
that I hope improves the UX of working on this scenario significantly:

- The dropdown shows the currently "active" project, which is determined
by:
  - Either the file you're currently editing
  - Or the file you have just recently switched to
  - Some example cases:
- If you are focused on file from project A but switch to project B in
the titlebar, nothing happens. However, as soon as you type on the file
from project A, the title bar will update and your active project will
return to being project A.
- If you're focused on file from project A and change tabs to a file
from project B, the title bar will update, showing project B as the
active one.
- The content you'll see in the branch picker will correspond to the
currently active project
- It's still possible to reach the "Recent Projects" picker through the
project dropdown
- It's possible to do all interactions (trigger dropdown, select active
project, and remove project from workspace) with the keyboard


https://github.com/user-attachments/assets/e2346757-74df-47c5-bf4d-6354623b6f47

Note that this entire UX is valid only for a multiple folder workspace
scenario; nothing changes for the single project case.

Release Notes:

- Workspace: Improved the UX of working with multiple projects in the
same workspace through introducing a project dropdown that more clearly
shows the currently active project as well as allowing you to change it.