Add package failure flags to Package Watchdog

This is a prerequisite for adding additional logging of
the Watchdog-triggered rollback reason. Add flags which
indicate the failure observed (native, crash, ANR, explicit
health check). These will be used in the future by
RollbackPackageHealthObserver to map the failure type to the
(new) set of available logging metrics.

Test: atest PackageWatchdogTest
Bug: 146415463
Change-Id: I7e7c5e5399011e2761dada2b989a95c2013307e9
Merged-In: I7e7c5e5399011e2761dada2b989a95c2013307e9
(cherry picked from commit f305f4de)