Refreshed UX for Audio Formats Setting [Backend]

This CL modifies getSurroundSound(reported=true) to always return formats
supported by device irrespective of mode.
This also adds unit tests to verify the APIs getSurroundSound and
setSurroundFormatEnabled.

Bug:171785330

Test: atest audiopolicy_tests
Test: Tested manually

Change-Id: Id309cc864fd380d7600c19e1839a63dd5756879f