Support routing audio playback to telephony uplink

This change enables phone apps to play audio to the uplink stream
during a call.
This change maks the AUDIO_OUTPUT_FLAG_INCALL_MUSIC_UPLINK flag to be added to the flags that are sent to the HAL when an ongoing call is active, the chosen output device is the TX telephony device, the stream type is music, and the calling app has the MODIFY_PHONE_STATE permission.
For this change to take place, the following changes were made to the signature of getOutputForAttr in IAudioPolicyService:
  1. Add pid (process id) parameter to getOutputForAttr.
  2. Make the flags parameter a pointer so changed value can be
  examined by calling function.

Bug: 69973354.
Test: tested manually.
Change-Id: I74cef3f8b66de6e0e8f87b6235130c2cdf423da7