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
diff --git a/services/audiopolicy/tests/AudioPolicyManagerTestClient.h b/services/audiopolicy/tests/AudioPolicyManagerTestClient.h
index bdddf06..433a6ff 100644
--- a/services/audiopolicy/tests/AudioPolicyManagerTestClient.h
+++ b/services/audiopolicy/tests/AudioPolicyManagerTestClient.h
@@ -121,6 +121,8 @@
 
     size_t getAudioPortListUpdateCount() const { return mAudioPortListUpdateCount; }
 
+    virtual void addSupportedFormat(audio_format_t /* format */) {}
+
 private:
     audio_module_handle_t mNextModuleHandle = AUDIO_MODULE_HANDLE_NONE + 1;
     audio_io_handle_t mNextIoHandle = AUDIO_IO_HANDLE_NONE + 1;