Fix regression in FBX import caused by Skeleton3D

[lyuma]

A change in commit f7fdc87 changed the Skeleton3D "pose" property from PROPERTY_USAGE_EDITOR to PROPERTY_USAGE_NOEDITOR.
This should have had no effect, however it turns out assimp was assigning to the pose property.

This change adjusts the FBX import to only get_bone_rest/set_bone_rest, not set_bone_pose

This PR supersedes #41490 - In other words, rather than undoing the cause of the regression, this attempts to fix the root cause in the old assimp FBX importer.

I have tested this on a poorly hand animated FBX, and can confirm that the second part of this patch appears to fix animation issues.

[lyuma]

Some comments for @RevoluPowered : This change is on Master because this regression that caused this issue is not yet present in the 3.2 branch. I understand that a fix has a chance of conflicting with a forward-port of #39418 to master, but if the bug is left unfixed, we both risk having a starting state that cannot be tested or compared against... The other thing, is that #39418 still assigns to pose (skeleton->set_bone_pose on modules/fbx/data/fbx_skeleton.cpp line 107:

print_verbose("working on bone: " + itos(bone_index) + " bone name:" + bone->bone_name);
skeleton->set_bone_rest(bone->godot_bone_id, get_unscaled_transform(bone->pivot_xform->LocalTransform, state.scale));
skeleton->set_bone_pose(bone->godot_bone_id, get_unscaled_transform(bone->pose_node, state.scale));

In order to test the effect of this on the FBX rewrite, I started with 3.2 backport by @fire of the Skeleton Inspector (available at https://github.com/fire/godot/tree/skeleton-inspector-3-2 ), and then merged @RevoluPowered #39418 (from https://github.com/RevoluPowered/godot/tree/feature/fbx_final_stage ).

After testing this change has on the FBX rewrite + new Skeleton class, I can confirm that the bug is present in the above code, and again, the fix is to remove the "set_bone_pose" function call. Here are the some screenshots against the same (proprietary) FBX file I have been using to test:

Before:

After:

Hence, this work should still be relevant for the FBX rewrite when it comes time to port to master. I do not think this needs to be addressed in the 3.2 branch, at least not yet.

[RevoluPowered]

we should really look how this works with the new importer too but this is OK for the assimp one

[RevoluPowered]

#40707 <-- 4.0 port of the FBX importer is here, but it's not got a lot of production fixes it needs from the 3.2 branch, I will update it soon once we resolve a bug found in the document parser.

[akien-mga]

Thanks!