Moving AWeb3Auth logic out of AActor for data persistence

[xynanlee]

Hi, nice work on the SDK. However, I think the method of implementation can be improved. Currently, the logic is mainly located in AWeb3Auth actor, being an AActor class, it will not survive a level change. If I have bound a logout event to AWeb3Auth at Main Menu, the actor will be destroyed when the level changes, and the delegate will be effectively unbounded. More so, I have to respawn the actor everytime the when I want to interact with Web3Auth after a level change.

I highly suggest moving the logic into GameInstanceSubsystem, so it can survive level changes.