Implement setProcessState() and scheduleTrimMemory()

This commit implements setProcessState() and scheduleTrimMemory() for
NativeApplicationThread. Respecting what ActivityThread does,
scheduleTrimMemory() calls the onTrimMemory callback when the process
is not in critical state or the specified trim level is not high enough.

Bug: 431632697
Bug: 431636312
Test: build and run cuttlefish
Flag: android.os.native_framework_prototype
Change-Id: Id1a0923ea859684cc3d47a090f49a4c11dcdf9af