Scoru,Proto: chunked internal transfers

Context

The goal is to facilitate the interoperability between the L1 and L2 contracts. Currently, the deposits are limited to 4Kb, which can be too short for complex calls in the L2. Fortunately, it's not really complicated to send a large deposit in chunks in the layer 1, we have the control on the inbox so we can put the chunks in the correct order so it's relatively easy to take care of them in the L2. Also note that even if this seems 'complicated', the L2 does not have to implement the reconstruction logic, it's up to them, if they need it or not.

The L1->L2 with this merge request can accept large messages, L2->L1 can be a bit more complicated and will definitely not be ready for O.

Manually testing the MR

If you want to go very deeply, you could write a small kernel that decodes the internal messages and reconstruct the payload. You can also try to do regular (small) deposits and assert that the behavior did not change (the tests should catch that).

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR