Remove `on_connecting` observer

- Steal `asset_loading` from `bevy_new_2d`
- Rename `BlockResources` to `BlockAssets`
- Remove `common::blocks::*` re-exports
- Turn `Args` into a resource and insert it
- Add `Screen` state to see when loading finishes
- Run gameplay systems only in `Gameplay` state
- Start server / connect when loading finishes

common/src/network/server.rs

@@ -35,7 +35,8 @@ impl Command for StartLocalServerCommand {
         world.spawn((
             Server::default(),
             Name::from("LocalServer"),
-            Started, // yeah it's started, alright
+            // NOTE: Inserting both makes the local-only server act properly.
+            (Linked, Started), // yeah it's started, alright
         ));
     }
 }