Static native plugins (systemd, clipboard, etc.) were being boxed as
Box<dyn Provider>, which lost access to the query() method needed for
submenu support. The Provider trait only has refresh() and items().
Add static_native_providers field to keep static native plugins as
NativeProvider instances, preserving their query() method. Update all
search methods and query_submenu_actions() to include this new list.
Fixes systemd plugin submenu not showing actions when selecting a service.
vikingowl
e23bdf5cee