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>
It does not make sense that the target actor is both destinatary
and content of the events being sent, so this API call is going away.
Since the event can be sent entirely unmodified (more so, it will
become immutable/readonly in the future), avoid creating a copy
since it does not matter sending one or other struct.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2216>
Even if activePage has been removed as part of commit 27627bd40, we've
still a reference of it in key press handler.
Given that there's no anymore an active page to redirect input to,
remove these references, so that can be handled in the proper view to
implement key-navigation.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1688>
