Merge "Implementation of IMS registration management APIs for SipTransport" am: 71a1997ce3

Original change: https://android-review.googlesource.com/c/platform/packages/services/Telephony/+/1527158

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: If51d4649c230b44659f047619e2459bcd0e0e289