Add support for editing resources

[randomPoison]

This implements basic support for receiving updated data for resources from the editor and applying those updates to the local state. Currently this is only implemented for resources, however the same pattern can be easily implemented for components.

• Split SyncResourceSystem into ReadResourceSystem and WriteResourceSystem.
• Add functionality to SyncEditorSystem to read incoming update data and dispatch it to the corresponding WriteResourceSystem.
• Add the requirement that registered resources be DeserializeOwned. We should add an API for registering read-only resources for when a resource only implements Serialize.
• Make some tweaks to the pong example so that changes to the ScoreBoard resource show up more immediately (useful for demo purposes).

Lots of easy ways to improve this, but I'd rather get this merged in with the functionality as-is. I'll write up some tickets to track the remainder of the cleanup work, that way others can have a chance to contribute.

[randomPoison]

Things I should probably still do before merging:

• Update docs for public types for sure, probably should also document any new/updated internal types.
• Fix the TODO for checking the source address for incoming packets.
• Add tests so that we can use CI to verify that the stuff like making the UDP socket non-blocking works correctly on all platforms.