Moving startObservingHealth API to PackageWatchdog

Based on the API review, moving the API to PackageWatchdog instead of
going through the observer route

Bug: 377888325
Test: TH
Flag: android.crashrecovery.flags.enable_crashrecovery
Change-Id: I50e6381ff947f4ec6324bca2292cb0562c34e7c0
2 files changed