Add support for freezing cached apps

Freeze apps when cached and unfreeze them once removed from the cache or
killed. Frozen apps will not use any CPU cycles, reducing power
consumption for misbehaving processes which might attempt to run
while cached.

Change-Id: Ib055352062825db62927015c33ee0a285aa4630c
Depends-On: pa/1495867, ag/9976279, ag/9981529, ag/9987868¬
Bug: 143308662
Test: manual, atest CachedAppOptimizerTest