Add support for interpolating skewed Transform2Ds

[aaronfranke]

Fixes #64252, supersedes #64418. Also adds a test case. See my comment at the bottom of #64418.

BugSquad Edited:
Fixes #71974

[TokageItLab]

I also commented in #64418 (comment), since 3D supports skew, so I suggest that the same fix is needed for Transform3D::interpolate_with as well for consistency.

[TokageItLab]

Personally, I agree with this fix. It is definitely better than the current broken Transform2D::interpolate_with(). But Transform3D::interpolate_with() still has a problem which discards skew, so it will be needed to be improved later on.

[akien-mga]

Thanks!