Add shell commands for app hibernation service

Add some shell commands to make it easier to test and tinker with app
hibernation service manually.

Bug: 175829330
Test: adb shell cmd app_hibernation set-state
com.google.android.deskclock true
adb shell cmd cmd app_hibernation get-state com.google.android.deskclock
Test: manual testing

Change-Id: I8fffd95288c65efedac55463c79b25f1252de260