audio: Cleanups and refactorings

Added utility functions for operating on positional
bit flags.

Moved retrieval of offload mix ports to ModuleConfig
utility class.

Clarify the names of read/write tests.

Bug: 205884982
Test: atest VtsHalAudioCoreTargetTest
Change-Id: Id20881c2e62bc1b95d8fc3c268f99e36337dce7a