32b9109967
Provide a reasonably public way to register and unregister search providers, without adding too much API. `Main.overview.searchController` provides access that may be generally useful, while `SearchController.addProvider()` and `SearchController.removeProvider()` provide a simple interface for extensions. Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2783>