Standard L2 Genesis: StandardBridge Changes

[tynes]

This ticket represents the changes to the StandardBridge per the standard L2 genesis spec. What this looks like in practice is removing the base StandardBridge from being initializable and instead only making the L1StandardBridge initializable. The network specific config in the L2StandardBridge is fetched from the L1Block contract rather than its storage. Given the L2StandardBridge is no longer initializable, doing upgrades with hardfork based transactions becomes more simple