Add the ability to send the feature tags associated with IMS registration

- In order to better support UCE, allow the IMS registration update to
the framework to include the feature tags associated with the registration
so that this information can be used in SIP PUBLISH.

- Encapsulate other IMS registration attributes into a singlular class.

Bug: 177375635
Test: atest CtsTelephonyTestCases:ImsServiceTest
Merged-In: Id730e5e0c9322c2a845523f3b3901f3d899c3f1c
Change-Id: Id730e5e0c9322c2a845523f3b3901f3d899c3f1c