Make BoneAttachment3D and Skeleton3D names consistent.

BoneAttachment3D nodes are now named as their bone name.
Resolves cases where BoneAttachment3D nodes will have arbitrary names like BoneAttachment3D6
Reserve the name "Skeleton3D" and use this name for all generated Skeleton3D nodes.

This change will break existing imported scenes with more than one skeleton and/or bone attachments.

modules/gltf/gltf_document.cpp

@@ -543,6 +543,7 @@ String GLTFDocument::_gen_unique_bone_name(Ref<GLTFState> p_state, const GLTFSke
 }
 
 Error GLTFDocument::_parse_scenes(Ref<GLTFState> p_state) {
+	p_state->unique_names.insert("Skeleton3D"); // Reserve skeleton name.
 	ERR_FAIL_COND_V(!p_state->json.has("scenes"), ERR_FILE_CORRUPT);
 	const Array &scenes = p_state->json["scenes"];
 	int loaded_scene = 0;
@@ -4471,7 +4472,7 @@ Error GLTFDocument::_create_skeletons(Ref<GLTFState> p_state) {
 		p_state->skeleton3d_to_gltf_skeleton[skeleton->get_instance_id()] = skel_i;
 
 		// Make a unique name, no gltf node represents this skeleton
-		skeleton->set_name(_gen_unique_name(p_state, "Skeleton3D"));
+		skeleton->set_name("Skeleton3D");
 
 		List<GLTFNodeIndex> bones;
 
@@ -5603,7 +5604,7 @@ void GLTFDocument::_generate_scene_node(Ref<GLTFState> p_state, Node *scene_pare
 		bone_attachment->set_owner(scene_root);
 
 		// There is no gltf_node that represent this, so just directly create a unique name
-		bone_attachment->set_name(_gen_unique_name(p_state, "BoneAttachment3D"));
+		bone_attachment->set_name(gltf_node->get_name());
 
 		// We change the scene_parent to our bone attachment now. We do not set current_node because we want to make the node
 		// and attach it to the bone_attachment
@@ -5694,7 +5695,7 @@ void GLTFDocument::_generate_skeleton_bone_node(Ref<GLTFState> p_state, Node *p_
 			bone_attachment->set_owner(p_scene_root);
 
 			// There is no gltf_node that represent this, so just directly create a unique name
-			bone_attachment->set_name(_gen_unique_name(p_state, "BoneAttachment3D"));
+			bone_attachment->set_name(gltf_node->get_name());
 
 			// We change the scene_parent to our bone attachment now. We do not set current_node because we want to make the node
 			// and attach it to the bone_attachment