more support for audio effect offload

Offloading of audio effects is now enabled for offloaded
output threads. If an effect not supporting offload is enabled,
the AudioTrack is invalidated so that it can be recreated in PCM
mode.

Fix some issues in effect proxy related to handling of effect
commands to offloaded and non offloaded effects.

Also fixed a bug on capture index in software Visualizer effect.

Bug: 8174034.

Change-Id: Ib23d3c2d5a652361b0aaec7faee09102f2b18fce