Eevee: Convert metallic nodes into princinpled nodes

And wipe metallic out of the map.

source/blender/blenkernel/intern/node.c

@@ -3594,7 +3594,6 @@ static void registerShaderNodes(void)
 	register_node_type_sh_add_shader();
 	register_node_type_sh_uvmap();
 	register_node_type_sh_uvalongstroke();
-	register_node_type_sh_eevee_metallic();
 	register_node_type_sh_eevee_specular();
 
 	register_node_type_sh_output_lamp();