Implement fork manager for L2

[rakanalh]

We need to implement a fork manager for:

• EVM upgrades
• Storage upgrades
• Guest code upgrades

[eyusufatik]

This is mostly for being able to revert state and reapply different soft confirmations.

Sort of a measure for when we need to do hard forks in the past etc.

The spec system is gonna be handled in #235 but the underlying storage should be able to fork.

• this will help with RPC not being able to acccess non-finalized state (in storage system terms is problematic) #813