feat(ops/auto-deploy): Support auto-deploy

Automatically rebuild the current system's NixOS config from the latest checkout
of depot.

Change-Id: I23aa7af50e16e985ac34df214e0905e770316e5e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4390
Reviewed-by: wpcarro <wpcarro@gmail.com>
Reviewed-by: zseri <zseri.devel@ytrizja.de>
Reviewed-by: grfn <grfn@gws.fyi>
Autosubmit: wpcarro <wpcarro@gmail.com>
Tested-by: BuildkiteCI

users/wpcarro/nixos/diogenes/default.nix

@@ -68,6 +68,11 @@ in {
       ];
     };
 
+    depot.auto-deploy = {
+      enable = true;
+      interval = "1h";
+    };
+
     journaldriver = {
       enable = true;
       logStream = "home";