Add functions to convert hashes to and from VRFVerKeyHash

[neilmayhew]

Description

Downstream projects are using a different type for these hashes, and don't need to make the role distinctions that ledger does. However, they do need to provide hashes of this type when passing various records to ledger. Providing conversion functions makes the code cleaner and safer in the downstream projects, because they don't have to import Cardano.Crypto.Hash and call castHash. The conversion functions provide a type-specialized wrapping of it.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages.
• Versions are updated in .cabal and CHANGELOG.md files.
• The version bounds in .cabal files for all affected packages are updated.
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[lehins]

👍