feat: Single player hosting in WebGL using RPC

[BenHamrick]

Expose the ability to use RPC especially on WebGL to allow us to easily make a single player mode while still using netcode usually as a host.

Changelog

• Added: The ability to use RPC using a property in the Transport.
• Changed: Allowed the ability to host a game if using RPC in WebGL to allow us to easily create a single player mode.

Testing and Documentation

• No tests have been added.
• No documentation changes or additions were necessary.

[CodeSmile-0000011110110111]

@BenHamrick Where is the RPCNetworkInterface type defined? I tried to add this change but cannot find such a class in the entire codebase, not even in your fork, and not on the Internet at large.

[BenHamrick]

@BenHamrick Where is the RPCNetworkInterface type defined? I tried to add this change but cannot find such a class in the entire codebase, not even in your fork, and not on the Internet at large.

My bad! It's supposed to be IPCNetworkInterface

[NoelStephensUnity]

@BenHamrick
You can opt to assign or create your own NetworkTransport that you switch to when running in a single player mode. You can make that implementation a "mock transport". You can see an example of a mock transport here.
Since you don't need any network connectivity in single player (other than services possibly which doesn't use UTP), all netcode related scripts should work. If you feel that this is not enough could you provide a working example for this PR so we can review it?

[BenHamrick]

@NoelStephensUnity I tried using the mock transport but it seems like NetworkManager.RealTimeProvider is private so the script won't work as is. Also seems a little extreme to require me to make a whole new transport to run my game in single player. Is there maybe a more complete example somewhere I can use without the private reference? I also fixed this branch to work now.