Add PassthruPatchRecord for low latency software patches

Implement a subclass of PatchRecord that uses PatchTrack's
thread for reading from HAL. This eliminates the need for
buffering that adds latency.

The only modification needed for PatchTrack is to indicate
unlimited amount of available frames to the playback thread.
This is to prevent PatchTrack from being deactivated by
DirectOutputThread due to lack of frames available.

RecordThread believes it reads audio data on its thread,
and manages timestamps as usual. The data that it "reads"
and passes to PassthruPatchRecord is discarded by the latter.

Bug: 117564323
Test: with MSD module
Merged-In: I376656e3c791e91e2196331ecdf2b425697c4e18
Change-Id: I376656e3c791e91e2196331ecdf2b425697c4e18