Add BLS key support

[palas]

Changelog

- description: |
    Added support for BLS keys.
  type:
    - feature
  projects:
    - cardano-api

Context

This works towards addressing the first part of: input-output-hk/ouroboros-leios#776

It adds a new kind of key (BLS), in order to be able to support key generation and hashing for this kind of key in cardano-cli. See PR: IntersectMBO/cardano-cli#1355

How to trust this PR

This follows the pattern for other keys, the only major decision is the usage of BLS12381MinSigDSIGN curve, instead of the other one. Also, you can test this code by using the CLI PR that is based in this PR: IntersectMBO/cardano-cli#1355

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff

[Copilot]

Pull request overview

Adds BLS12-381 (MinSig) key support to cardano-api so downstream tooling (e.g., cardano-cli) can generate, serialise, and hash BLS keys.

Changes:

• Introduces a new internal BlsKey type with Key, Bech32, raw-bytes, CBOR, and text-envelope instances.
• Extends SomeAddressVerificationKey to include BLS verification keys in rendering/mapping/deserialisation.
• Exposes BlsKey (and AsBlsKey) via Cardano.Api.Key and wires the new module into the Cabal library.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
cardano-api/src/Cardano/Api/Key/Internal/SomeAddressVerificationKey.hs	Adds a BLS constructor and includes it in Bech32 rendering/mapping/deserialisation.
cardano-api/src/Cardano/Api/Key/Internal/Leios.hs	New module defining BlsKey and associated instances for serialisation and hashing.
cardano-api/src/Cardano/Api/Key.hs	Re-exports BlsKey and AsBlsKey in the public API.
cardano-api/cardano-api.cabal	Exposes the new Cardano.Api.Key.Internal.Leios module.

[Jimbo4350]

Can you add some haddocks describing what this key is for?