Add new IRegistrationManager for managing IMS registration

Restructure registration API to allow for MMTEL and RCS to
both manage registration callbacks as well as provide new
query APIs for registration state and transport type.

Bug: 122098288
Test: atest GtsTelephonyTestCases
Merged-In: Ia568dcd059c2bcef26462e808088901edf6b072f
Change-Id: Ia568dcd059c2bcef26462e808088901edf6b072f