Make run take self instead of &mut self

[90degs2infty]

Currently, running a game driver is backed by GameDriver::run(&mut self) -> ....

This has a set of drawbacks:

• a GameDriver drives exactly one game, therefore lending towards the signature GameDriver::run(self) -> ...
• it forces us to apply Jone's trick internally to alter the internal state, as we cannot move out the state member when having access to a &mut self

The underlying assumption was that with the self signature, terminating the running driver would be hard/impossible and storing the GameDriver would be hard, too. This is probably not the case when using the Abortable future. Check this.