After final improvements to the official formatter implementation,
this commit now performs the first treewide reformat of Nix files using it.
This is part of the implementation of RFC 166.

Only "inactive" files are reformatted, meaning only files that
aren't being touched by any PR with activity in the past 2 months.
This is to avoid conflicts for PRs that might soon be merged.
Later we can do a full treewide reformat to get the rest,
which should not cause as many conflicts.

A CI check has already been running for some time to ensure that new and
already-formatted files are formatted, so the files being reformatted here
should also stay formatted.

This commit was automatically created and can be verified using

    nix-build https://github.com/infinisil/treewide-nixpkgs-reformat-script/archive/a08b3a4d199c6124ac5b36a889d9099b4383463f.tar.gz \
      --argstr baseRev b32a0943687d2a5094a6d92f25a4b6e16a76b5b7
    result/bin/apply-formatting $NIXPKGS_PATH

nix run nixpkgs#silver-searcher -- -G '\.nix$' -0l 'description.*"[Aa]n?' pkgs \
  | xargs -0 nix run nixpkgs#gnused -- -i '' -Ee 's/(description.*")[Aa]n? (.)/\1\U\2/'

According to Nixpkgs manual[1] and NixOS 23.11 Release Note[2], the
`sourceRoot` attribute passed to `stdenv.mkDerivation` should be
specified as `"${src.name}"` or `"${src.name}/subdir"` when `src` is
produced using `fetchgit`-based fetchers.

`sourceRoot = "source"` or `sourceRoot = "source/subdir"` is based on
the assumption that the `name` attribute of these pre-unpacked fetchers
are always `"source"`, which is not the case. Expecting constant `name`
also makes the source FODs prone to irrelevent hashes during version
bumps.

[1]: https://nixos.org/manual/nixpkgs/unstable/#var-stdenv-sourceRoot
[2]: https://nixos.org/manual/nixos/stable/release-notes#sec-release-23.11