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/python-modules/wxPython/3.0.nix

@@ -6,7 +6,7 @@
 , libX11
 , wxGTK
 , wxmac
-, pkgconfig
+, pkg-config
 , buildPythonPackage
 , pyopengl
 , isPy3k
@@ -35,7 +35,7 @@ buildPythonPackage rec {
 
   hardeningDisable = [ "format" ];
 
-  nativeBuildInputs = [ pkgconfig ]
+  nativeBuildInputs = [ pkg-config ]
     ++ (lib.optionals (!stdenv.isDarwin) [ wxGTK libX11 ])
     ++ (lib.optionals stdenv.isDarwin [ wxmac ]);
 

pkgs/development/python-modules/wxPython/4.0.nix

@@ -2,7 +2,7 @@
 , stdenv
 , buildPythonPackage
 , fetchPypi
-, pkgconfig
+, pkg-config
 , which
 , cairo
 , pango
@@ -34,7 +34,7 @@ buildPythonPackage rec {
 
   doCheck = false;
 
-  nativeBuildInputs = [ pkgconfig which doxygen ]
+  nativeBuildInputs = [ pkg-config which doxygen ]
   ++ (if stdenv.isDarwin then [ wxmac ] else [ wxGTK ]);
 
   buildInputs = [ ncurses libintl ]

pkgs/development/python-modules/wxPython/4.1.nix

@@ -3,7 +3,7 @@
 , fetchPypi
 , buildPythonPackage
 , which
-, pkgconfig
+, pkg-config
 , python
 , isPy27
 , pyopengl
@@ -30,7 +30,7 @@ buildPythonPackage rec {
   # https://github.com/wxWidgets/Phoenix/issues/1316
   doCheck = false;
 
-  nativeBuildInputs = [ which doxygen wxGTK pkgconfig ];
+  nativeBuildInputs = [ which doxygen wxGTK pkg-config ];
 
   buildInputs = [
     wxGTK.gtk