Silc Lizard (Tokage) Renew

Rebased & fixed. @reduz I think that it is ready to go. Preview (please turn on volume): https://user-images.githubusercontent.com/61938263/179770012-5c42cb75-95de-4650-a824-ada7d53dd673.mp4 test project: [volume_blend_test.zip](https://github.com/godotengine/godot/files/9141665/volume_blend_test.zip)

@reduz Do you think that it is the right way to simply remove this implicit volume overwrite and implement a log-scale adjustable volume interface in StreamPlayer and let the user...

@reduz I mean, why not just have the user explicitly create a track called `[ValueTrack]AudioStream:Volume`? There is no need for BlendTree to change the volume of the AudioStream internally, and...

@reduz Do you mean caching and playing back multiple audio source in one AudioStream and adjust volume? That is currently not possible, but at least I think that this implicit...

@reduz It may indeed be necessary to change to a lower layer to get the blending correctly, but this PR is necessary for cases where we do not want to...

May be related by #48432.

As a first step, we need to refactor the implementation of cubic_interpolate(). Currently, they are duplicated in Vector2, Vector3 and Animation. It should be implemented as one of the Math...

The approach @lyuma described was to insert a bone to cancel the transform further into the parent of the bone root and keep parent node transform, but I disagree. That...

After discussions with @lyuma and @fire, we have reached an agreement that this PR has a different purpose than #60115 and that both can be implemented. #60115 feature is intended...

Yes, it is my todo to document retargeting and changed blend animations after the feature freezes.