Add modernized tox environments/linting

[athornton]

Also...this ran the formatter, so it's a huge change.

[athornton]

@rufuspollock This is a very boring but very large changeset. Most of it is formatting (a lot of trailing whitespace deleted, some stuff that black did).

I've got the scaffolding in place to do Ruff (which Rubin is moving to in order to supplement Black), but it's very opinionated and will take a while to incorporate...Likewise there's the framework to generate changelogs from commit messages and to parse versions from git (which will let us eventually tag a release and push a build).

While our settings for black are basically "79 columns and Python 3.11, please", there's a whole lot configured for Ruff (it's in pyproject.toml) that's representative of the way my group in Rubin works, but might or might not be what you want for the Giftless project. Likewise with the mypy settings there as well, but those are (I think) more likely to just be unused here than something you actively don't want.

[rufuspollock]

@athornton ok let's get this merged 😄

[athornton]

Cool....I'm working on a queue of things now that really tighten up the type hinting, and get rid of the separate ini files for the most part (moving configuration under pyproject.toml).