CodeMirror Blob: support fuzzy finder

Created by: olafurpg

Fixes #40509 (closed)

Previously, the fuzzy finder was not activated when using the Mod-k shortcut while the CodeMirror blob view was focused.

This PR only moves existing code around. The diff is modestly large because we had to move the fuzzy finder state to the toplevel Layout component and drill it down to the search bar and the blob view (which has a long path from the layout component).

Test plan

See the CI go green. I manually verified the change works as expected by triggering Cmd+k while having the CodeMirror blob view focused.

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.