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/applications/graphics/renderdoc/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, cmake, pkgconfig, mkDerivation
+{ lib, stdenv, fetchFromGitHub, cmake, pkg-config, mkDerivation
 , qtbase, qtx11extras, qtsvg, makeWrapper
 , vulkan-loader, libglvnd, xorg, python3, python3Packages
 , bison, pcre, automake, autoconf, addOpenGLRunpath
@@ -28,7 +28,7 @@ mkDerivation rec {
   ]; # ++ (with pythonPackages; [pyside2 pyside2-tools shiboken2]);
   # TODO: figure out how to make cmake recognise pyside2
 
-  nativeBuildInputs = [ cmake makeWrapper pkgconfig bison pcre automake autoconf addOpenGLRunpath ];
+  nativeBuildInputs = [ cmake makeWrapper pkg-config bison pcre automake autoconf addOpenGLRunpath ];
 
   postUnpack = ''
     cp -r ${custom_swig} swig