nixos/automatic-timezoned: Fix boot delays and systemd unit ordering

Since the service sets `WantedBy=default.target`, `graphical.target`
ends up waiting for it to complete. Since `geoclue.service`, which
*this* service depends on, in turn depends on `network-online.target`,
this ends up making full boot wait for network availability.

This is obviously unintended; The unit should have always had an
`After=default.target`.

Furthermore, the systemd docs recommend depending on specifically
`multi-user.target` *or* `graphical.target`, rather than
`default.target`. In practice, on a default NixOS system, using
`default.target` delays starting this service until a graphical
session starts - this is obviously not ideal, since it makes sense to
update the timezone on a non-graphical system as well, so we fix that
while we're at it.

nixos/modules/services/system/automatic-timezoned.nix

@@ -57,13 +57,16 @@ in
       automatic-timezoned = {
         description = "Automatically update system timezone based on location";
         requires = [ "automatic-timezoned-geoclue-agent.service" ];
-        after = [ "automatic-timezoned-geoclue-agent.service" ];
+        after = [
+          "automatic-timezoned-geoclue-agent.service"
+          "multi-user.target"
+        ];
         serviceConfig = {
           Type = "exec";
           User = "automatic-timezoned";
           ExecStart = "${cfg.package}/bin/automatic-timezoned";
         };
-        wantedBy = [ "default.target" ];
+        wantedBy = [ "multi-user.target" ];
       };
 
       automatic-timezoned-geoclue-agent = {
@@ -77,7 +80,6 @@ in
           Restart = "on-failure";
           PrivateTmp = true;
         };
-        wantedBy = [ "default.target" ];
       };
 
     };