Part of https://github.com/zed-industries/zed/issues/1153
Closes https://github.com/zed-industries/community/issues/1326

<img width="432" alt="image"
src="https://github.com/zed-industries/zed/assets/2690773/a50ee073-9d2e-4e5c-ae5e-23312693c540">

Adds an `project_panel::NewSearchInDirectory` action ("alt-shift-f"
default) in the project editor context to open a new project search in
the selected directory.

Release Notes:

- Adds an action to open project search in the project panel's directory