fixed conflict between tracks have same name different type in the AnimationTree cache

[TokageItLab]

Fixed #48526.
Fixed #43848.

An animation will no longer be stuck implicitly as long as the single animation is played in the animation.

However, when some tracks conflict in the one animation, or when blending animations of different track types that will set the same value, only the track with the later iteration order will be played, regardless of the blend value. For example, the blending of ValueTrack and BezierTrack is not yet working correctly (so it's been like that for a while). This may need to be fixed in the future. See #49431. ValueTrack and BezierTrack are can be blended by latest commit. Fixed #49431. (But BlendShape Track and TRS Track are not so.)

[TokageItLab]

Self considering. I thought it was fine to cache MethodTrack and AudioTrack separately.

However, currently, for Transform3D, Value, and Bezier, the changes are stored in the TrackCache in each TrackType without blending. To solve #49431, we need a way to convert, blend and combine them into one in the cache.

[TokageItLab]

BezierTrack and ValueTrack can now be blended together. However, the subpath must match.

For example,

[BezierTrack]
Node2D:position:x
Node2D:position:y

and

[ValueTrack]
Node2D:position:x
Node2D:position:y

will be blended, but

[ValueTrack]
Node2D:position

will not be blended.

The above case can be seen in the demo project.

track_blends_2.zip

If you want to solve the matching problem, we will need to do a huge refactoring.

Currently, we can't tell from the subpath name "x" whether it is a Vector2 or Vector3, so we need to do a search every frame, every ValueTrack with a subpath, by tracing the parent of the NodePath and actually getting the value of the path and checking the type.

[TokageItLab]

Some methods has been outdated; superseded by #56902.

[TokageItLab]

I managed this in #56902, but reduz is not that positive about retargeting at least for 4.0, so I don't know if it will be merged by 4.0 or not.
In the meantime, I will salvage these for bug fixes separately from that.

[TokageItLab]

Salvaged and rebased.

[TokageItLab]

Closing this once since it is out of date. The inability to blend BezierTrack and ValueTrack can be made a documentation issue, but I think it needs to be taken care of in cases of path conflicts such as AudioTrack and MethodTrack.