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

Updated to 49a3ee4801cf64f479e3f0bad839a5dd8e5b4932

`dhallPackages.callPackage` can provide the `Prelude` package directly,
and this change uses that to simplify the build for `dhall-grafana`

At init, dhall-grafana would not compile because it has a dependency
on Prelude version 19.  Upstream merged a patch to bring it's Prelude
dependency up to nixpkgs.

Fixes https://github.com/NixOS/nixpkgs/issues/138374

The build failure in the above issue is due to
`pkgs.dhallPackages.dhall-packages` transitively depending on an
older Prelude version (12.0.0) that is incompatible with newer
Dhall versions.

I first attempted to upgrade `pkgs.dhallPackages.dhall-packages`, but
that failed due to a bad hash on an internal import, so I'm removing
the build instead.