audio policy: refactor audio source client descriptor

Make the SourceClientDescriptor carry the information that it
is used for call TX ot TX patch instead of relying on the comparison
with mCallRxSourceClient and mCallTxSourceClient.

Flag: EXEMPT mechanical refactoring
Bug: 292492229
Test: make
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ccbd787b3eab93e8cf8ac7698ab007db4f65eb32)
Merged-In: I60f07bab8092046df717eb934846534c7c97dc37
Change-Id: I60f07bab8092046df717eb934846534c7c97dc37