MSRV 1.84

[clarfonthey]

This is the version where Cargo's MSRV resolver was added, so, it was what was decided previously as a good place to bump to. Includes clippy fixes for methods that were added in the meantime that could be used instead.

I also took the liberty of running taplo fmt in the repo to clean up the TOML files. I can revert this if desired.

In preparation for 2024 edition compatibility, I have enabled the unsafe_op_in_unsafe_fn lint and ensured it passes here, since that's the largest change that edition 2024 would have. I've done my best to try and minimise the unsafe block bounds auto-added by fixes as well as possible, but there's a lot of code that needs to be annotated with safety comments anyway, so, some are left with very large unsafe blocks.

Additionally, I have made unreachable_pub now warn by default as agreed upon in #675. With a higher MSRV, we can avoid false positives.

Note that 1.85 was when edition 2024 was added, so, it might also be desirable to bump to that, but with this PR, the changes to do so are minimal and just require cargo fmt.

[clarfonthey]

We probably could have removed incompatible_msrv here for a while; this now understands that a nightly feature means that you're not going to be following MSRV.

[clarfonthey]

-D clippy::all has a higher priority than the various lints in Cargo.toml, so, this ends up ignoring our lint preferences to allow some lints, but -D warnings does what we want here.

[clarfonthey]

Rather than enable the lint group here, I decided to just manually add these lints to the list since it avoids lint group priority issues. Since this is 2018 idioms, I doubt that the group will gain any new additions any time soon.

[clarfonthey]

Side note: I hate that you can't lint code that's been cfg'd out. I know that this is nothing new, but it's frustrating that something as simple as unsafe-op-in-unsafe-fn requires downloading multiple builds of libstd, recompiling dependencies for multiple targets, and potentially even downloading separate linking tools for other targets all because of this limitation. I've done it for multiple different cases but this is just the latest one and I'm annoyed about it and going to vent about it here.

Thanks for coming to my talk.

[clarfonthey]

I think at this point, I've implemented all major changes up to the MSRV that I think are important before merging. If I've missed any, please feel free to mention it, although as usual, no rush. I'm not going to have a proper computer to dev this for the next couple days, so, I'll get to any requests when I'm back home unless I happen to notice them before I go to bed tonight.