This commit was created by a combination of scripts and tools:
- an ast-grep script to prefix things in meta with `lib.`,
- a modified nixf-diagnose / nixf combination to remove unused `with
lib;`, and
- regular nixfmt.

Co-authored-by: Wolfgang Walther <walther@technowledgy.de>

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

https://redwax.eu/dist/rs/ChangeLog-mod_timestamp-0.2.3

continuation of #109595

pkgconfig was aliased in 2018, however, it remained in
all-packages.nix due to its wide usage. This cleans
up the remaining references to pkgs.pkgsconfig and
moves the entry to aliases.nix.

python3Packages.pkgconfig remained unchanged because
it's the canonical name of the upstream package
on pypi.

Part of: https://github.com/NixOS/nixpkgs/issues/108938

meta = with stdenv.lib;

is a widely used pattern. We want to slowly remove
the `stdenv.lib` indirection and encourage people
to use `lib` directly. Thus let’s start with the meta
field.

This used a rewriting script to mostly automatically
replace all occurances of this pattern, and add the
`lib` argument to the package header if it doesn’t
exist yet.

The script in its current form is available at
https://cs.tvl.fyi/depot@2f807d7f141068d2d60676a89213eaa5353ca6e0/-/blob/users/Profpatsch/nixpkgs-rewriter/default.nix