Revert "Revert "Add remote callbacks for persistent vr mode""

This reverts commit 2abf1c60.

We need the ability to register remote callbacks for persistent vr mode,
so vr flinger can register for persistent vr mode events.

Bug: 35885165

Test: Manually confirmed vr flinger can register and receive persistent
vr mode events.

Change-Id: I7713c4c8acae9a369fd0c06695ef712fddd12be8