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.
I've extracted some of libraries and made expression simpler.
(cherry picked from commit 66e6f99d40350a4b2a235913a1fa77d88b1a44a6)
Signed-off-by: Domen Kožar <domen@dev.si>
