Load shortucts concurrently with app target resolution

Reload shortcuts whenever we rebuild the target list:
 * in ChooserActivity#onHandlePackageChange(), called by system package
   change broadcast, target pinning, and ResolverActivity#onRestart;
 * in work profile status broadcast receiver.

Tie ShorctuLoader to a Lifecycle (instead of exposing lifecycle
methods i.e. destroy) and switch to coroutines from executors.
Add a startup-to-first-shortcut tracing and a debug log.

Bug: 262927266
Test: manual testing, unit tests.
Change-Id: Iaa4bd9a88f29378d75d88b2ea8fc3698cbd3be8f
6 files changed