voice processing: support several sessions per input stream

Bug: 128419018
Test: CTS AudioPreProcessingTest, manual tests for VoIP calls and
camcorder.

Change-Id: I5fe39451c30889e8abd56a16ddbb6bdf378ef2f2
(cherry picked from commit f69b0d0f1b2f3ea236961ca2c15ef8bec8087f26)
1 file changed