Fix lost focus when navigating back in project search result (#22483)
Closes #22447
When navigate forward/back, the focus moves from the ProjectSearchView's
result editor to the Pane, and then move to the ProjectSearchView, but
the event `on_focus_in` not triggered for ProjectSearchView, causing the
result editor to lose focus eventually.
https://github.com/zed-industries/zed/blob/f6dabadaf79bd29c89c8d55a1e9f1d33236f736e/crates/workspace/src/workspace.rs#L1372
https://github.com/zed-industries/zed/blob/f6dabadaf79bd29c89c8d55a1e9f1d33236f736e/crates/workspace/src/workspace.rs#L1385
Considering that the navigation might be triggered again in the next
frame, so use `on_next_frame` in `on_focus` event to move focus to
result editor.
Next frame:
- the blur event triggered for result editor.
- focus move from ProjectSearchView to result editor in `on_focus` event
for ProjectSearchView
- navigate again, focus moves from result editor to Pane then move back
to ProjectSearchView
- the focus not change during this frame, so no focus event happened for
ProjectSearchView.
Release Notes:
- Fix lost focus when navigate back in project search result
Co-authored-by: Kirill Bulatov <kirill@zed.dev>
