Adds 2 new contracts to the `L2` directory. Both contracts
extend OZ `Ownable` such that the `onlyOwner` modifer logic is
overwritten.

`CrossDomainOwnable` is designed for ownership of contracts on L2
when the communication goes directly through the `OptimismPortal`.
This is not safe for when the communication goes through the
`CrossDomainMessenger` system, as `msg.sender` would be the
address of the `L2CrossDomainMessenger` and if that is the owner
of the L2 contract then anybody going through the messenger system
would have owner permissions on the contract.

`CrossDomainOwnable2` is designed for ownership of contracts on L2
when the communication goes through the messenger system. It checks
for the L1 message sender value that is set in the
`L2CrossDomainMessenger` contract.

Both of these contracts include test coverage and are relatively simple.

contracts-bedrock: review fixes

contracts-bedrock: make the messenger value constant

contracts: fix

contracts-bedrock: update snapshot

lint

fix test