Modify the api definition in the ImsMedia HAL for AV sync

For more accurate calculation of incoming packet latency and improved inter-media synchronization, modify the AVSync API's request to use the RTCP-SR report's NTP timestamp. This absolute timestamp facilitates cross-media comparisons.

Bug: 321878340
Test: mm
Change-Id: I9980ac832095d1caf82c42e17307c83522de4b3e