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.
This solves the dependency cycle in gcr alternatively so there won't be
two gnupg store paths in a standard NixOS system which has udisks2 enabled
by default.
NixOS users are expected to use the gpg-agent user service to pull in the
appropriate pinentry flavour or install it on their systemPackages and set
it in their local gnupg agent config instead.
Co-authored-by: Florian Klink <flokli@flokli.de>
