am: Delegate process freeze state updates to callback

The logic for determining and applying process freeze and unfreeze
actions has been moved from `OomAdjuster.updateAppFreezeStateLSP`
to `OomAdjusterCallback.onProcessFreezabilityChanged`.

This refactoring improves modularity by delegating `CachedAppOptimizer`
interactions and related freezing logic to the `OomAdjusterCallback`.

Bug: 441178013
Test: m services.core
Test: atest MockingOomAdjusterTests OomAdjusterTests
Test: atest FrameworksServicesTestsRavenwood_ProcessStateController
Flag: EXEMPT PURE_REFACTOR

Change-Id: Ic70e34771a3af230cbf77bd2805035a255b276ce