Dal/Refutation: add functions produce/verify_proof

Context

This MR implements needed functions (produce_proof and verify_proof) to integration Dal refutation in Scoru. The three main commits introduce:

• the proof type
• the implementation of function produce_proof
• the implementation of function verify_proof

Unit tests are currently in MR !6405 (merged) (which is now merged into this MR)

Manually testing the MR

$ dune exec src/proto_alpha/lib_protocol/test/unit/main.exe -- test "^\[Unit\] dal slot proof$"

$ dune exec src/proto_alpha/lib_protocol/test/pbt/test_dal_slot_proof.exe

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