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/libarchive/default.nix

@@ -1,5 +1,5 @@
 {
-  fetchFromGitHub, stdenv, pkgconfig, autoreconfHook,
+  fetchFromGitHub, stdenv, pkg-config, autoreconfHook,
   acl, attr, bzip2, e2fsprogs, libxml2, lzo, openssl, sharutils, xz, zlib, zstd,
 
   # Optional but increases closure only negligibly. Also, while libxml2
@@ -23,14 +23,14 @@ stdenv.mkDerivation rec {
 
   outputs = [ "out" "lib" "dev" ];
 
-  nativeBuildInputs = [ pkgconfig autoreconfHook ];
+  nativeBuildInputs = [ pkg-config autoreconfHook ];
   buildInputs =
     stdenv.lib.optional stdenv.hostPlatform.isUnix sharutils
     ++ [ zlib bzip2 openssl xz lzo zstd ]
     ++ stdenv.lib.optionals stdenv.isLinux [ e2fsprogs attr acl ]
     ++ stdenv.lib.optional xarSupport libxml2;
 
-  # Without this, pkgconfig-based dependencies are unhappy
+  # Without this, pkg-config-based dependencies are unhappy
   propagatedBuildInputs = stdenv.lib.optionals stdenv.isLinux [ attr acl ];
 
   configureFlags = stdenv.lib.optional (!xarSupport) "--without-xml2";