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/tracker/default.nix

@@ -4,7 +4,7 @@
 , gettext
 , meson
 , ninja
-, pkgconfig
+, pkg-config
 , asciidoc
 , gobject-introspection
 , python3
@@ -57,7 +57,7 @@ stdenv.mkDerivation rec {
     meson
     ninja
     vala
-    pkgconfig
+    pkg-config
     asciidoc
     gettext
     libxslt
@@ -68,7 +68,7 @@ stdenv.mkDerivation rec {
     docbook_xml_dtd_45
     python3 # for data-generators
     systemd # used for checks to install systemd user service
-    dbus # used for checks and pkgconfig to install dbus service/s
+    dbus # used for checks and pkg-config to install dbus service/s
   ];
 
   buildInputs = [