Expose interpolation methods for 3D track in Animation class

[TokageItLab]

Animation::value_track_interpolate() is already exposed, but not for TRS3D/BlendShape tracks. They need to return an error internally to check for compression/decompression outside of interpolate().

Now we expose these wrapper functions for GDScript.

// Internal functions.
Error _position_track_interpolate(int p_track, double p_time, Vector3 *r_interpolation) const;
Error _rotation_track_interpolate(int p_track, double p_time, Quaternion *r_interpolation) const;
Error _scale_track_interpolate(int p_track, double p_time, Vector3 *r_interpolation) const;
Error _blend_shape_track_interpolate(int p_track, double p_time, float *r_blend) const;

// Bound functions.
Vector3 position_track_interpolate(int p_track, double p_time) const;
Quaternion rotation_track_interpolate(int p_track, double p_time) const;
Vector3 scale_track_interpolate(int p_track, double p_time) const;
float blend_shape_track_interpolate(int p_track, double p_time) const;

[SaracenOne]

I think this looks good. Sorry I wasn't able to look at this for 4.0, but as discussed in the channel, I think we'll be able to get this in in a small point release.

[YuriSizov]

This needs a rebase.

Also, we shouldn't rename the public method to have an underscore. You say those are "internal", but they are used throughout the codebase. Bound methods, on the other hand, don't need to be public, and can start with the underscore.

[TokageItLab]

Rebased.

Renamed public core methods as follow:

Error _position_track_interpolate(int p_track, double p_time, Vector3 *r_interpolation) const;

to

Error try_position_track_interpolate(int p_track, double p_time, Vector3 *r_interpolation) const;

[akien-mga]

Thanks!