Grant FGS cpu_time capability by default

All FGS should be granted cpu_time to achieve parity with the current
implementation of mShouldNotFreeze.

Stricter behavior has been moved to the prototype flag which is meant to
have more aggressive policies and is still under development.

Flag: com.android.server.am.use_cpu_time_capability
Flag: com.android.server.am.prototype_aggressive_freezing

Test: atest FrameworksMockingServicesTests:MockingOomAdjusterTests

Bug: 370817323
Bug: 370798593

Change-Id: If9a7d991bf94d9ce5de6775c6c2d1f52de53efef