[Standard L2 Genesis] Enable generation of the L2 Genesis file from previous releases.

[maurelian]

Ultimately this should be moved to the superchain-registry, but for now it will need to be done by tracking bytecode in a solidity library.

As outlined here:

The genesis script should work as follows:

1. check to see if a fork is configured
2. if no, use dev bytecode with vm.getDeployedCode()
3. if yes, use the library to get the hardcoded bytecode