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/libraries/v8/default.nix

@@ -1,5 +1,5 @@
 { stdenv, lib, fetchgit, fetchFromGitHub
-, gn, ninja, python, glib, pkgconfig, icu
+, gn, ninja, python, glib, pkg-config, icu
 , xcbuild, darwin
 , fetchpatch
 }:
@@ -101,7 +101,7 @@ stdenv.mkDerivation rec {
   # to be exceeded
   NIX_CFLAGS_COMPILE = stdenv.lib.optionalString stdenv.cc.isGNU "-Wno-class-memaccess";
 
-  nativeBuildInputs = [ gn ninja pkgconfig python ]
+  nativeBuildInputs = [ gn ninja pkg-config python ]
     ++ stdenv.lib.optionals stdenv.isDarwin [ xcbuild darwin.DarwinTools ];
   buildInputs = [ glib icu ];
 

pkgs/development/libraries/v8/plv8_6_x.nix

@@ -4,7 +4,7 @@
 # 2019-08-29, nixpkgs does not have v8 6.x, and v8_5 is bumped to 5.4.232, which
 # is a bit outdated.  plv8 3.x is planned to support v8 7.x
 
-{ stdenv, lib, fetchgit, fetchFromGitHub, gn, ninja, python, glib, pkgconfig
+{ stdenv, lib, fetchgit, fetchFromGitHub, gn, ninja, python, glib, pkg-config
 , doCheck ? false
 , snapshot ? true
 }:
@@ -158,7 +158,7 @@ stdenv.mkDerivation rec {
         use_custom_libcxx_for_host=false
   '';
 
-  nativeBuildInputs = [ gn ninja pkgconfig ];
+  nativeBuildInputs = [ gn ninja pkg-config ];
   buildInputs = [ python glib ];
 
   buildPhase = ''