Regression on master on Godot ik.

[fire]

Godot version

d956904

System information

Win11, RTX 3000 series

Issue description

Master regressed on SkeletonModifierStack3D.

The arms are not taking rest pose in the calculation. (Animation now have to include rest pose).

#53765

@TwistedTwigleg

Steps to reproduce

This character broken when IK is enabled. res://skeleton_modification/scenes/skeleton_test_08_character_full/Skeleton_Test_08.tscn

Minimal reproduction project

https://github.com/TwistedTwigleg/Godot_GSOC_2020_Project

[TwistedTwigleg]

I'll take a look once I can and see if I can get it working again 👍

[TwistedTwigleg]

I started working on a fix and made a draft PR #53821. FABRIK is the only modifier not working currently in the draft PR and I'll try to see if I can get it working fully once I can. 👍

(Side note: I'm not sure regression is a proper tag for this, as it seems like it's a normal bug caused by the compatibility breaking changes in #53765, but I digress)