Added support for not registering for RR events by default

We historically used to register any user subscribing to display changes
via DisplayManager::registerDisplayListener for refresh rate changes.
Going forward, this behaviour is being changed to subscribe them to refresh rate changes only when they explicitly request for it

Bug: 391828526
Flag: com.android.server.display.feature.flags.delay_implicit_rr_registration_until_rr_accessed
Test: atest DisplayEventTest
Change-Id: If218ba7b49f11ca369aee76230b4ea0a28469a68