Make PackageWatchdog variables configurable

We leverage DeviceConfig to configure the following variables:
    watchdog_trigger_failure_duration_millis
    watchdog_trigger_failure_count
    watchdog_explicit_health_check_enabled
    watchdog_explicit_health_check_timeout_millis

Fix PackageWatchdogTest accordingly.

Bug: 129335707
Test: added Log to PackageWatchdog that prints the received
value from DeviceConfig and made sure it matches the expected
Test: atest com.android.server.PackageWatchdogTest
Merged-In: I8a57b87682a4c636a61afdd7f93700459ccfddeb

Change-Id: I8a57b87682a4c636a61afdd7f93700459ccfddeb