refactor(flake)!: deduplicate code in configurations flake module

Pass around `perSystem`'s `pkgs` instances to the system configurations
Some more refactoring in `configurations`' `mkHost` functions
Also start using `home-manager`'s `useGlobalPkgs` option
Also use `mkShellNoCC` for default `devShell`
Also `nix flake update`

shells/default.nix

@@ -1,8 +1,7 @@
 # If pkgs is not defined, instanciate nixpkgs from locked commit
 { pkgs ? (import ../nixpkgs.nix) { }
 , inputs
-, outputs
 , ...
 }: {
-  default = import ./default { inherit pkgs inputs outputs; };
+  default = import ./default { inherit pkgs inputs; };
 }

shells/default/default.nix

@@ -1,9 +1,8 @@
 # Shell for bootstrapping flake-enabled nix and other tooling
 { pkgs
 , inputs
-, outputs
 , ...
-}: pkgs.mkShell {
+}: pkgs.mkShellNoCC {
   NIX_CONFIG = ''
     extra-experimental-features = nix-command flakes
   '';