[3.x] Fix error when having BoneAttachment before PhysicalBone

[timothyqiu]

Fixes #42010

bind_child_node_to_bone() allows re-adding an existing bind. But unbind_child_node_from_bone() does not have extra checks for unbinding a non-existing bindings. So List::erase() complains about erasing something that does not exist.

There's no error when no BoneAttachment node comes before a PhysicalBone. This is because calling List::erase() on an empty list won't print an error. (Bone attachments are also bind to bones, so when there's a bone attachment node before the physical bone, the bind node list is not empty when it enters tree.)

It's inconsistent that List::erase() behaves differently when empty and non-empty. But I think fixing this on Skeleton level is acceptable since we prefer local solutions 😛

There're no such methods on master.

[lawnjelly]

Might be worth reviewing at the same time whether this should be a List at all versus a LocalVector. There's a whole bunch of stuff in Godot using Lists that really should be LocalVectors (due to linked lists being so bad for cache etc). At some point it would be nice to go through these.

[timothyqiu]

Updated and replaced the List with LocalVectori.

[lawnjelly]

Are the nodes_bound required to be in order? If not, we can maybe use remove_unordered().. 🤔

[timothyqiu]

Skeleton itself does not require some specific order. But changing nodes_bound order affect the order of the returned array from get_bound_child_nodes_to_bone() and the bound_children property. So using remove_unordered() might break user code I think.

[akien-mga]

Thanks!

[timothyqiu]

Cherry-picked for 3.5.2