Allow DEFAULT_INPUT_METHOD to capture audio during RTT call

The UID of the current InputMethodService (DEFAULT_INPUT_METHOD) is
pushed from AudioService to AudioPolicyService via AudioSystem.
Allow capture audio if:
- the UID is the current InputMethodService's UID,
- AND a RTT call is active,
- AND the source is AUDIO_SOURCE_VOICE_RECOGNITION.

Bug: 147037345
Test: use voice input with Gboard 9.1.4 during a simulated RTT call.
Change-Id: Ib32ec25e962833eddd0320742e177e3c1e0e5c05