Crypto/Blake2B: add an alternative functor that export conversion functions

What

Add Blake2B.Make_minimal_with_data functor that exports the conversion functions.

Why

Using Blake2D to hash values of a given length will be useful to produce reproducible trace_id for OpenTelemetry. It avoids instantiating the full functor with Base58 when it is not needed.

How

Simply re-export Blake2B.Make_minimal into another functor.

Manually testing the MR

Let's considering it as refactoring.

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