Clarify Consensus vs Policy with Interop Access Lists

[tynes]

Follow up to #612

The specs should better clarify the usage of access lists to make it really clear that it is not a consensus thing. It is purely validated at the transaction ingress/mempool, not as part of the state transition function. It is also possible to check during block building time, but there are still executing message logs, so we need to optimize the block building path in the future.