treewide: pkgs.pkgconfig -> pkgs.pkg-config, move pkgconfig to alias.nix

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.

pkgs/development/compilers/factor-lang/default.nix

@@ -1,5 +1,5 @@
 { stdenv, fetchurl, glib, git,
-  rlwrap, curl, pkgconfig, perl, makeWrapper, tzdata, ncurses,
+  rlwrap, curl, pkg-config, perl, makeWrapper, tzdata, ncurses,
   pango, cairo, gtk2, gdk-pixbuf, gtkglext,
   mesa, xorg, openssl, unzip }:
 
@@ -19,7 +19,7 @@ stdenv.mkDerivation rec {
     ./fuel-dir.patch
   ];
 
-  buildInputs = with xorg; [ git rlwrap curl pkgconfig perl makeWrapper
+  buildInputs = with xorg; [ git rlwrap curl pkg-config perl makeWrapper
     libX11 pango cairo gtk2 gdk-pixbuf gtkglext
     mesa libXmu libXt libICE libSM openssl unzip ];