Overhaul many things

[NickCrews]

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See CHANGELOG.md for the big-picture of what has changed.

Hopefully this isn't too overwhelming. Each commit individually is pretty small and probably understandable. First I would read the CHANGELOG for a high level, and then just browse through each commit individually, they pretty much are self-explanatory. Occasionally I forgot to adjust a test or documentation at the same time as the actual change, but then I went back later and corrected them.

See https://github.com/NickCrews/pyusps/actions?query=branch%3Areturn-errors for an example of what the CI runs look like.

[NickCrews]

@thelinuxkid here is a PR, let me know if this is too big for you to look at at once, I can cut it down into smaller PRs if so. Thanks for taking a look!

[thelinuxkid]

Thanks Nick. Give me a few days to take a look at this.