Move PM cache invalidate inside mlock

Bug: 181992565

Ensure that the PM cache invalidation occurs inside regions protected
by the PM mlock.  Recent changes guard the invalidation so that it
occurs only if something really changed - this limits the number of
invalidation calls and makes it lower overhead.

Create a new marker class for the PM lock, similar to the marker class
ActivityManagerGlobalLock.  The marker class has no performance impact
but it enables future snapshot improvements using lock injection.

The result is tested with a special build that checks the snapshot
invalidation flag every time the PM lock is taken.  The test verifies
that the invalidation flag is false (meaning the snapshot is valid)
every time the lock is taken, which means that invalidation occurs
only under control of mLock.

Test: atest
 * FrameworksServicesTests:AppsFilterTest
 * FrameworksServicesTests:PackageInstallerSessionTest
 * FrameworksServicesTests:PackageManagerServiceTest
 * FrameworksServicesTests:PackageManagerSettingsTests
 * FrameworksServicesTests:ScanTests
 * FrameworksServicesTests:UserSystemPackageInstallerTest
 * PackageManagerServiceBootTest
 * UserLifecycleTests#startUser
 * UserLifecycleTests#stopUser
 * UserLifecycleTests#switchUser
 * android.appsecurity.cts.EphemeralTest
 * android.appsecurity.cts.InstantAppUserTest

Change-Id: I96154fbee78b620c76a2b7d8614bc433fc61e911