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/warnings/integer_division.gd

@@ -0,0 +1,10 @@
+func test():
+	# This should emit a warning.
+	var __ = 5 / 2
+
+	# These should not emit warnings.
+	__ = float(5) / 2
+	__ = 5 / float(2)
+	__ = 5.0 / 2
+	__ = 5 / 2.0
+	__ = 5.0 / 2.0