Improved UDP socket binding

Currently we require that the application logic manually create and bind a UDP socket and add it to the world as a resource. This gives the user control over what port the socket is bound to, but ultimately exposes UDP as an implementation detail that we don't want to finalize on.

Instead, we should have the `EditorSyncSystem` create its own UDP socket, and add a way to configure which port it binds to. By default it should let the system decide what port it binds to (by binding to `0.0.0.0:0`), but allow the user to specify a different port/address to bind to. It might also be good to allow the user to override the default port via an environment variable.