cubic_interpolate() and cubic_slerp() cause overshoot

[TokageItLab]

Godot version

4.0.dev, 3.4

System information

Any

Issue description

#40592 split and resend. Current cubic_interpolate() causes overshoot; we should consider employing modified-akima interpolation.

References of modified-akima:

• https://slpr.sakura.ne.jp/qp/akima-interpolation/
• https://jp.mathworks.com/help/matlab/ref/makima.html

Steps to reproduce

2022-02-11.9.39.40-1.mov

Minimal reproduction project

cubic_interpolation_test.zip

[TokageItLab]

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 functions.