Audio effects: test API for Spatializer effect

Add the Spatializer UUID to the test API so the presence of
the effect, and the expected Spatializer immersive audio
level, can be detected in tests.

Bug: 383216552
Test: atest android.media.audio.cts.SpatializerTest#testEffectSpatializer
Flag: EXEMPT bug fix with TestApi
Change-Id: Ie7a47041d28e491f9cba2c7cec81c1502628df8d