GDScript: Improve call analysis

* Add missing `UNSAFE_CALL_ARGUMENT` warning.
* Fix `Object` constructor.
* Display an error for non-existent static methods.

modules/gdscript/tests/scripts/runtime/features/stringify.gd

@@ -24,7 +24,8 @@ func test():
 	print(StringName("hello"))
 	print(NodePath("hello/world"))
 	var node := Node.new()
-	print(RID(node))
+	@warning_ignore("unsafe_call_argument")
+	print(RID(node)) # TODO: Why is the constructor (or implicit cast) not documented?
 	print(node.get_name)
 	print(node.property_list_changed)
 	node.free()