Considering prototypeAggressiveFreezing in test

The assignment of implicit_cpu_time can change depending on
the state of prototypeAggressiveFreezing.
Also adding the missing annotation to enable the base
cpu_time-capability flag.

Flag: com.android.server.am.prototype_aggressive_freezing

Test: atest FrameworksMockingServicesTests:MockingOomAdjusterTests

Bug: 370798593

Change-Id: Ibeb200c08e67e10da0a862273bddb0619095fe8d