Network improvements

[rxyyy]

This issue contains all the required network improvements for the Leipzig milestone.

Unique Machine Identifiers

The server should only allow 1 client connection per system.

• The client should generate a unique machine identifier.
• The server should check if the machine identifier exists before accepting a connection.

Data Validation

The server should parse any available AttribSys data exported into YML files using using heyitsleo's Attribulator and verify various network requests with it.

• Vehicle creation requests should check if the vehicle exists.
• Race lobby creation requests should check if the event exists and is compatible with the selected options.

Race Lobbies

The functionality shown in NFSCO - Race Sync? will be brought back in the form of race lobbies.

Race lobbies will have the following set of options on initial creation.

• Toggle traffic spawning.
• Toggle police spawning.
• Toggle vehicle collisions.
• Toggle vehicle NOS usage.
• Set the number of laps for looping events.
• Set a password.
• Set the maximum amount of clients for events other than canyon duels.
• Set the minimum and maximum client vehicle tier.
• Restrict the use of specific vehicle classes.

Race lobbies require the following game-related changes.

• Disable post-race boss flow when playing online.
• Disable skipping NISes when playing online.
• Replace Game_InitRacers.
• Ensure all clients have finished loading before removing the loading screen in order to synchronize the NIS.