Test removing a user immediately after starting it in background.

Check device is not crashed when user data directory is deleted
while some other processes might still be trying to access those
deleted files.

This CL also isolates test methods by waiting for broadcast barrier.

Bug: 264540191
Bug: 290324382
Bug: 233240023
Test: atest FrameworksServicesTests:com.android.server.pm.UserLifecycleStressTest#removeRecentlyStartedUserStressTest
Change-Id: Iacd916d608edcffe6ba0560c39e6e822e8bd1a37