Pull in nightly rust-fmt, use vid rustfmt.toml

[pls148]

Old HS repo used to have nightly rustfmt. After some discussion in the monorepo channel, I figured we'd try nightly rustfmt to get better grouping of dependencies. This gets rid of the mess of redundant "use hotshot_types::a::b::some thing".

Tested locally with nix/direnv. Not sure if I got other peoples' use cases.

The main changes are to the following files:

• flake.nix
• rust-toolchain.toml
• rustfmt.toml

The rest of the changes were done by rustfmt picking up the new config.

[sveitser]

Looks great thanks.

For next time, making a commit first with the changes and a separate commit for the formatting makes it easier to review because the reviewer can check out the first commit and run just fmt then diff against the branch HEAD. I did this manually now which (still) seemed a lot easier than reading at the diff.

One question, hotshot had group_imports = "StdExternalCrate" which we don't have here. I think that's quite nice. Any particular reason for excluding it?

[pls148]

Looks great thanks.

For next time, making a commit first with the changes and a separate commit for the formatting makes it easier to review because the reviewer can check out the first commit and run just fmt then diff against the branch HEAD. I did this manually now which (still) seemed a lot easier than reading at the diff.

One question, hotshot had group_imports = "StdExternalCrate" which we don't have here. I think that's quite nice. Any particular reason for excluding it?

Ah good catch, yeah I liked that one too. Added to this PR!