Proto: Unreveal tz4 for S

What

tz4 addresses use the signing scheme BLS, with proof of possession. Starting in S, this proof should be included at reveal time. To ensure already revealed tz4 addresses also include a proof of possession, they will simply be unrevealed for S, requiring a new reveal operation to be forged after the migration.

Why

How

This is done lazily by matching on the addresses, and doing some encoding magic.

Manually testing the MR

A test has been included, it can be launched with dune exec tezt/tests/main.exe -- --file protocol_migration.ml -m "protocol migration for reveal"

Another way to test it manually is to do a manual migration test, but revealing one tz4 before and after the migration (this is what the tezt test does, but a manual test would be possible with a mainnet context for instance).

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