Flagging ThemeOverlayController and ThemeManagerService

ThemeOverlayController is being replaced by ThemeManagerService so not it is under a flag provided by ThemeModule.java. The new ThemeManagerService is now being initialized under the flag in SystemServer

This CL also updates ActivityManagerService to make sure it does not wait for ThemeOverlayController initialization when ThemeManagerService is active.

Bug: 333694176
Test: atest FrameworksServicesTests_theme
Flag: android.server.enable_theme_service
Change-Id: Iaeb0f458b5bb17afdbb94d87ef1ba06b7402e02c