chore: bump Rust edition and various infra cleanups

[JustSoup312]

• Bumps Rust version to 2024
• Runs cargo fmt on the tree
• Adds deny.toml
• Adds rustfmt.toml
• Sets MSRV as defined by cargo msrv

[Arnavion]

I'm not really sold on most of this.

Definitely don't want the rustfmt change. Its defaults are bad and I don't care to hunt down the configs that will fix it and maintain them in perpetuity, especially since when I tried that in the past many of them were unstable.

Don't care for cargo deny; I don't use it, and there's only one dep anyway. I'd rather not add more cargo-install'd deps. In fact even machete is only there because it's part of my default template, but it's pointless when there's only one dep and the crate is tiny, so I'll remove it too.

Don't really want the MSRV change. Even if it does compile with that old version (I assume you picked it because it's the one that introduced E2024), I have no intention of "S"upporting anything that old when even upstream doesn't.

lints sections shouldn't have been deleted. CI won't assert those lints now.

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I've updated the edition to 2024 (and remove the workaround for the one clippy bug since it's fixed now). If you really want the other changes, you're welcome to say why.