nodePackages: move to nodejs-14_x

NodeJS 12.x will not be supported when we release 22.05.

https://nodejs.org/en/about/releases/

pkgs/development/node-packages/composition.nix

@@ -2,7 +2,7 @@
 
 {pkgs ? import <nixpkgs> {
     inherit system;
-  }, system ? builtins.currentSystem, nodejs ? pkgs."nodejs-12_x"}:
+  }, system ? builtins.currentSystem, nodejs ? pkgs."nodejs-14_x"}:
 
 let
   nodeEnv = import ./node-env.nix {

pkgs/development/node-packages/generate.sh

@@ -3,7 +3,7 @@ set -eu -o pipefail
 cd "$( dirname "${BASH_SOURCE[0]}" )"
 node2nix=$(nix-build ../../.. -A nodePackages.node2nix)
 rm -f ./node-env.nix
-${node2nix}/bin/node2nix -i node-packages.json -o node-packages.nix -c composition.nix
+${node2nix}/bin/node2nix -i node-packages.json -o node-packages.nix -c composition.nix --pkg-name nodejs-14_x
 # using --no-out-link in nix-build argument would cause the
 # gc to run before the script finishes
 # which would cause a failure