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/property_setter_getter.gd

@@ -0,0 +1,37 @@
+# 4.0+ replacement for `setget`:
+var _backing: int = 0
+var property:
+	get:
+		return _backing + 1000
+	set(value):
+		_backing = value - 1000
+
+
+func test():
+	print("Not using self:")
+	print(property)
+	print(_backing)
+	property = 5000
+	print(property)
+	print(_backing)
+	_backing = -50
+	print(property)
+	print(_backing)
+	property = 5000
+	print(property)
+	print(_backing)
+
+	# In Godot 4.0 and later, using `self` no longer makes a difference for
+	# getter/setter execution in GDScript.
+	print("Using self:")
+	print(self.property)
+	print(self._backing)
+	self.property = 5000
+	print(self.property)
+	print(self._backing)
+	self._backing = -50
+	print(self.property)
+	print(self._backing)
+	self.property = 5000
+	print(self.property)
+	print(self._backing)