Ensure listener is not triggered when reregistered

Ensure a listener is not reregistered a second time.
Ensure the listener does not get a repeat value.
Update the javadocs for addGlobalWindowViewsListener to clear up
confusion. Fix some typos.

Flag: android.view.flags.root_view_changed_listener
Bug: 401234449
Test: atest CtsViewTestCases
Change-Id: Icaaee0db756884f90409e07c0f088b04afba4ce3