add audio routing policy configuration to audio service

- audio routing policy is read from config.xml.
- There can be multiple policy and AUDIO_HW_VARIANT property
  chooses which one to use.
- added mocking test to verify the policy setting.

bug: 25126797

Change-Id: Ia9d6fad90f6536dddd79a56be514f6f3afb56270
(cherry picked from commit 1e1fdf6387b0ec4333c0d06a21b8f482590db3aa)
9 files changed