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_inheritance.gd

@@ -0,0 +1,33 @@
+# Test deeply nested class architectures.
+class Test:
+	var depth = 1
+
+	class Nested:
+		var depth_nested = 10
+
+
+class Test2 extends Test:
+	var depth2 = 2
+
+
+class Test3 extends Test2:
+	var depth3 = 3
+
+
+class Test4 extends Test3:
+	var depth4 = 4
+
+	class Nested2:
+		var depth4_nested = 100
+
+
+func test():
+	print(Test.new().depth)
+	print(Test2.new().depth)
+	print(Test2.new().depth2)
+	print(Test3.new().depth)
+	print(Test3.new().depth3)
+	print(Test4.new().depth)
+	print(Test4.new().depth4)
+	print(Test.Nested.new().depth_nested)
+	print(Test4.Nested2.new().depth4_nested)