Arbitrary expression injection in Pillow

PIL.ImageMath.eval in Pillow before 9.0.0 allows evaluation of arbitrary expressions, such as ones that use the Python exec method ImageMath.eval("exec(exit())").

While Pillow 9.0.0 restricted top-level builtins available to PIL.ImageMath.eval(), it did not prevent builtins available to lambda expressions. These are now also restricted in 9.0.1.