gpui: Add `is_action_available_in` function (#45029)

This compliments the `window.is_action_available` function that already
exists.

Release Notes:

- N/A
3a013d8090Anthony Eid committed on 12/16/2025, 10:03:30 PM· committed by GitHubparentab4cd95
1 file changedLine totals unavailable