BlendTree implicitly forces overwriting of AudioStream volume when AudioTrack is used

[TokageItLab]

Godot version

4.0.dev

System information

Any

Issue description

I had sent a PR as #55218, but after discussion with @reduz we agreed that this needs to be implemented at a lower layer, so I am closing the PR and reposting it as an issue for tracking.

In a BlendTree, AudioTrack will change the volume of the AudioStreamPlayer implicitly when blending. This is useful for damping sounds like footsteps, but it can be a problem if you want to play sound effects with NodeOneshot, or if you are controlling the volume externally.

https://www.youtube.com/watch?v=0ztTcX7Z-Do

If we want to place a reverberating sound effect at the end of an animation like the video above, the current implementation requires a work-around that uses MethodTrack, which makes AudioTrack quite unusable.

Steps to reproduce

Place the sound effect at the end of the animation with AudioTrack and blend the animation with the OneShot node.

Minimal reproduction project

audio_track_test.zip