refactor: make hash and eq non recursive

[tobymao]

No description provided.

[georgesittas]

Was this benchmarked? I've two branches where I refactored the implementations as well (2 different ways), but they were slower compared to our current implementation and we decided to not use them.

Will review tomorrow, haven't checked whether/how they're different from the approach here.

[tobymao]

Yea, it could be faster. It also leverages caching in better ways. So it should make the optimizer way faster too.

[georgesittas]

Nice work. I'd add this test as well to demonstrate that the PR solves the issue:

    def test_hash_large_asts(self):
        # Ensures we can actually compare large ASTs and not fail due to exceeding recursion limit
        ast = parse_one("SELECT 1 UNION ALL " * 500 + "SELECT 1")
        assert isinstance(hash(ast), int)