Use communication device callback and fix reinitialization routing

This CL replaces the speaker broadcasts with using the provided
AudioManager onCommunicationDeviceChanged callback in order to listen to
updates to the communication device. This is done with the hope of
seeing improved performance with when Telecom receives indication of
when the speaker toggles on/off. We have seen cases where when the
speaker is toggled on/off quickly, the broadcasts can be received out of
order and cause Telecom to show the audio route as speaker when audio is
routing to earpiece, for example. This occurs as a result of switching
from earpiece -> speaker -> earpiece and Telecom receiving SPEAKER_ON
after SPEAKER_OFF.

There is also a fix done to ensure that the audio routing is
reinitialized at the end of the call. We've gotten reports from user
that if the audio is routed to speaker and another call is placed, then
there is an audio flicker from speaker to earpiece in the UI at the
beginning of the call.

Bug: 353419513
Bug: 371625143
Flag:
com.android.server.telecom.flags.new_audio_path_speaker_broadcast_and_unfocused_routing
Test: Added unit test for verifying call audio route reintialization
Test: Manual to confirm that onCommunicationDeviceChanged callback is
being received for speaker phone switches. Tested with switching between
earpiece, speaker, and LEHS.

Change-Id: If51cc560791cbc81734a2ff6e3e57067910531cb