Adds a removeChangeListener to FeatureFlags$BooleanFlag.

This will help us avoid leaks, etc.

Also changes ENABLE_SMARTSPACE_ENHANCED back to a DeviceFlag

Bug: 181194850
Bug: 181077020
Test: atest NexusLauncherOutOfProcTests:com.android.launcher3.memory.MemoryTests -- --abi armeabi-v7a
Change-Id: I6f54af3e6b6302a073b8b7d448ff72b05a803d8f
2 files changed