[DO NOT MERGE] [MEL] Changes to Rollup and OSP contracts

[TucksonDev]

!! WIP - DO NOT MERGE !!

Note

This is a preliminary version, and can completely change, based on changes in the design or the implementation of the feature in nitro.

This PR contains changes to support MEL in the Rollup and OSP contracts.

Key changes

• The target of the next assertion to create is not an Inbox position anymore. We now use the hash of the block previous to where the current assertion is created
• Onchain inbox accumulators are not used anymore, so now assertions are hashed only using the previous assertion hash and the current assertion data
• GlobalState contains now 4 new fields:
  • MELState hash
  • Next message hash
  • Msg count
  • Executed Msg count
• Setting a new MELConfig in the Rollup config allow it to set a new Inbox and SequencerInbox

Pending work

• Overflowing assertions
• nextParentChainBlockHash to use on initialization
• Rollup update process
• OSP contracts

Nitro reference PRs

• BoLD with MEL changes nitro#4643