Store RTT transcript message received when UI is in background.

If the call disconnects when RTT UI is in background, any messages received from remote should be saved to transcript. RttCallPrensenter might not be available at this point, so the job is done inside DialerCall#onRemovedFromCallList

Bug: 78576798
Test: presubmit
PiperOrigin-RevId: 194821868
Change-Id: I10381b1c292f918763360c7a4bcd0470250f2293
4 files changed