Add enable_private_space_features flag check for Private Space implementation

Bug: 326060689
Test: atest FrameworksMockingServicesTests:com.android.server.pm.UserManagerServiceTest
Test: atest IntentForwarderActivityTest
Test: Manual
Change-Id: Ia636758df0a5b6f63cb58933265d6b436aac67e1
6 files changed