Add dozens of new integration tests to the GDScript test suite

This also ignores `.out` files in the file format static checks.

modules/gdscript/tests/scripts/parser/features/class.gd

@@ -0,0 +1,25 @@
+# Test non-nested/slightly nested class architecture.
+class Test:
+	var number = 25
+	var string = "hello"
+
+
+class TestSub extends Test:
+	var other_string = "bye"
+
+
+class TestConstructor:
+	func _init(argument = 10):
+		print(str("constructor with argument ", argument))
+
+
+func test():
+	var test_instance = Test.new()
+	test_instance.number = 42
+
+	var test_sub = TestSub.new()
+	assert(test_sub.number == 25)  # From Test.
+	assert(test_sub.other_string == "bye")  # From TestSub.
+
+	TestConstructor.new()
+	TestConstructor.new(500)