chore: add GUT test framework

addons/gut/scratch/demo_missing_defaults.gd

@@ -0,0 +1,15 @@
+extends SceneTree
+
+# Created for https://github.com/godotengine/godot/issues/66218
+func mixed_example(p1, p2 = {}, p3 = "a", p4 = 1, p5 = []):
+	pass
+
+
+func _init():
+	var script = load('res://scratch/demo_missing_defaults.gd')
+	var methods  = script.get_script_method_list()
+	for m in methods:
+		print('-- ', m.name, ' (', m.default_args.size(), ')')
+		print(JSON.stringify(m, '  '))
+
+	quit()