Sanity check: Ensure AST hasn't changed

[grigorescu]

Black has some interesting thoughts about checking that the AST hasn't changed after re-formatting to ensure that the code is semantically equivalent: https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#ast-before-and-after-formatting

Reformatting shouldn't introduce semantic changes, so I think this would be more of a double-check on the correctness of zeekscript itself.