Remove pydantic and switch to dataclasses/validobj

[virtuald]

Over the years pydantic has annoyed me in various different ways. I'd like to switch to dataclasses, and use validobj for validation instead.

Doing this for the meson rewrite, but interested in feedback.

[auscompgeek]

Curious what you find annoying specifically? We've still yet to update to pydantic 2.

[virtuald]

pydantic has broken at least once or twice over the years, and I feel like there's just been little things that have bubbled up to a general annoyance. I've come to really like dataclasses, so I prefer a solution that can just leverage them. validobj is really simple, and it works.