nixos/autosuspend: init at version 4.3.0

`autosuspend` is a daemon that periodically runs user-defined checks to
verify whether the system should be suspended.  It's already available
in nixpkgs.  This adds a NixOS module which starts the daemon as a
systemd service.

Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>

nixos/modules/module-list.nix

@@ -571,6 +571,7 @@
   ./services/misc/atuin.nix
   ./services/misc/autofs.nix
   ./services/misc/autorandr.nix
+  ./services/misc/autosuspend.nix
   ./services/misc/bazarr.nix
   ./services/misc/beanstalkd.nix
   ./services/misc/bees.nix