audio: Implementation of audio I/O, part I

This patch adds necessary structures and prepares for implementing
data flow for audio I/O.

Also in this patch we clarify the relationship between audio patches
and buffer size for audio I/O, and between buffer size and latency.

Bug: 205884982
Bug: 233816848
Test: atest VtsHalAudioCoreTargetTest
Change-Id: I8522632607d4cf50a112225c19b5dd5ad8848591