Use structs in the server browser

[uniboi]

implements the changes from R2Northstar/NorthstarLauncher#453 and adds callbacks when connecting to a server via UI to allow mods to track which server has been joined

void function AddConnectToServerCallback( void functionref( ServerInfo ) callback )

Registers a new callback; throws an error if the same callback is being registered twice

void function RemoveConnectToServerCallback( void functionref( ServerInfo ) callback )

Remove a callback

void function TriggerConnectToServerCallbacks()

Triggers all connection callbacks

[GeckoEidechse]

Quick skim and oh damn, this looks so much nicer than what we have rn 👀

[F1F7Y]

Code looks good, works in testing