This adjusts the solution in
https://github.com/zed-industries/zed/pull/4014 to fix the double-focus
issue, allowing each pane's project search to work independently.

Release Notes:

- Changed the name of the `workspace::DeploySearch` action to
`pane::DeploySearch` and changed it's behavior to open a new search OR
focus an existing project search in the current pane.
(https://github.com/zed-industries/community/issues/2395)