Fix GDNative wrapper type sizes (RID, Variant, Packed*Array), add size checking static asserts.

modules/gdnative/gdnative/node_path.cpp

@@ -37,6 +37,8 @@
 extern "C" {
 #endif
 
+static_assert(sizeof(godot_node_path) == sizeof(NodePath), "NodePath size mismatch");
+
 void GDAPI godot_node_path_new(godot_node_path *r_dest, const godot_string *p_from) {
 	NodePath *dest = (NodePath *)r_dest;
 	const String *from = (const String *)p_from;