Add VTS tests for audio effects

Added tests covering IEffect, IEqualizerEffect, and
ILoudnessEnhancer interfaces.

Minor corrections in the interface definitions and implementations:

 - fixed descriptions and @callflow annotations in IEffect;

 - fixed type used for band levels in IEqualizerEffect;

 - fixed specification of frequencies in IEqualizerEffect;

 - fixed some bugs in previously non-execrices Effects code;

 - warning messages changed to error messages.

Test: this is a test
Bug: 32022706
Change-Id: I0e0bc111b07d944ad8a0321e8b1ec703f8d1a73e