Receiving side Call handover API implementation.

Bug: 65415068
Test: Manual

Design doc:
https://docs.google.com/document/d/1qY3oAzjff_4A1ttYb_CGrE_OwTRmXMG_KGsIuPT1ey8/edit#Bug:

Change-Id: Ic0c4af19098252389648007628affc19a44f89dd
Merged-in: Ic0c4af19098252389648007628affc19a44f89dd