Update the PlatformCompat cache in OomAdjuster when gets notified

...instead of reading from PlatformCompat when it hits an obsoleted
cache at critical code path in oomAdjUpdate.

The cache will also be refreshed when the ApplicationInfo is updated.

Bug: 192316054
Test: atest FrameworksServicesTests:OomAdjusterTests
Test: atest ActivityManagerPerfTests:OomAdjPerfTest
Change-Id: I4d826a84770fa3b83752b11851d261e41acc2c16