Add pitch and volume to audio in animations

[killzebug]

Makes audio in animations use the pitch and volume properties of the AudioStreamPlayer they're played from.
Fixes: #91605

[TokageItLab]

This is not correct fix and the wrong way to go about it.

The problem is that the AudioStreamPlayer properties are being ignored in the playback within AudioStreamPolyphonic, so AudioStreamPolyphonic needs to be fixed, not AnimationMixer.

Then, since AudioTrack is played back by AudioStreamPolyphonic, we need to add a feature to AudioTrackKey to allow it to set volume and pitch for each of them individually. And Instead of passing AudioStreamPlayer properties, we need to pass them individually from the key.

Simply put, AudioStreamPlayer properties should be treated as properties of the master track, and AudioTrackKeys should have properties for individual streams; It may be divided into two PRs as "Fix AudioStreamPlayer doesn't affect pitch and volume property to AudioStreamPolyphonic (bugfix)" and "Add volume and pitch property to AudioTrack key (enhancement)".