refactor: Proper gas token setup

[LHerskind]

The current gas token setup only works because nothing is real.

The rollups "gas token" is disconnected from anything that is actually deposited into the rollup, e.g., fully separate balance. The rollup contract should NEVER have a balance. A bridge will have a balance, and it will talk to the bridge, but that is kinda it.

Also need to consider the setup for upgrades.