By switching to the tools bundled within nixpkgs we can provide a much
more "pure" development environment that doesn't randomly change over
time.
Previously we would be using the latest and greatest version of the
formatting and linting tools while our development environment only
offered whatever was in the (old) nixpkgs pin. Nowadays we have all the
tools we need in nixpkgs and can thus use those instead. By following
nixpkgs more closely we can make sure to make use of those tools in this
project as well. Hopefully removing the "yearly churn" of doing big
migrations.
For the meantime I allowed the upper case acronyms check (and a few
other minor lints) in the clippy configuration. This will allow a
smoother transition towards the newer clippy code that is decoupled from
the actual linting changes.
This fixes the `Unable to process command
'::add-path::/nix/var/nix/profiles/per-user/runner/profile/bin'
successfully.` errors (this was deprecated by GitHub).
Also fix alignment, to ease copy-pasting.
