Switch project search deploy behavior to be isolated to a pane (#4072)

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)

crates/workspace/src/pane.rs

@@ -99,6 +99,7 @@ actions!(
         CloseItemsToTheLeft,
         CloseItemsToTheRight,
         GoBack,
+        DeploySearch,
         GoForward,
         ReopenClosedItem,
         SplitLeft,