Revisit CCF crypto interfaces (mostly RSA/EC keys)

[maxtropets]

Resolves #6673

• Break RSA->EC inheritance
• Rename PublicKey -> ECPublicKey, KeyPair -> ECKeyPair, etc
• No more common public key, ccf::crypto::KeyVariant provided for explicit handing of different key types

✅ Long Test passed
☑️ AB perf: no regression

Mainly involved changes in RSA, other survived with no functional changes, the interface surface remains the same (except naming).

This's how it looks for RSA (and others, with probably extra non-exported files for historical reasons)

    ccf::crypto::RSAPublicKey          ccf::crypto::RSAKeyPair
               |                                  |
               |                                  |
               v                                  |
    RSAPublicKey_OpenSSL                          |
               |                                  |
               |                                  v
               └─────────────────────→  RSAKeyPair_OpenSSL
                                         (private_openssl)

[Copilot]

Pull Request Overview

This PR refactors the crypto API to explicitly separate EC (Elliptic Curve) and RSA key types, improving type safety and API clarity. The main changes include renaming PublicKey to ECPublicKey and KeyPair to ECKeyPair, removing problematic inheritance between RSA and EC key types, and introducing a KeyVariant type for handling different key types explicitly.

• Renamed core EC crypto types: PublicKey → ECPublicKey, KeyPair → ECKeyPair
• Separated RSA and EC key type hierarchies to eliminate error-prone inheritance
• Introduced KeyVariant template for explicit handling of different key types
• Updated RSA API to use explicit padding parameters and unified method names

Reviewed Changes

Copilot reviewed 75 out of 75 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
include/ccf/crypto/key_variant.h	New file introducing KeyVariant template for handling different key types
include/ccf/crypto/ec_key_pair.h	Renamed from key_pair.h, now specifically for EC keys
include/ccf/crypto/ec_public_key.h	Renamed PublicKey class to ECPublicKey
include/ccf/crypto/rsa_key_pair.h	Updated RSA API to inherit from RSAPublicKey, unified method names
include/ccf/crypto/rsa_public_key.h	Added RSAPadding enum, removed inheritance, unified verify API
include/ccf/crypto/verifier.h	Updated to use KeyVariant for storing different key types
src/crypto/verifier.cpp	Implemented verify methods with KeyVariant handling
src/crypto/openssl/ec_key_pair.*	Renamed from key_pair.*, implementation for EC keys
src/crypto/openssl/ec_public_key.*	Renamed from public_key.*, implementation for EC public keys
src/crypto/openssl/rsa_public_key.*	Refactored to remove inheritance, unified verify API with padding
src/crypto/openssl/rsa_key_pair.*	Updated to inherit from RSAPublicKey_OpenSSL
src/crypto/key_pair.cpp	Deleted, moved to ec_key_pair.cpp
src/crypto/rsa_key_pair.cpp	Deleted, moved into openssl/rsa_key_pair.cpp
src/endpoints/authentication/jwt_auth.cpp	Updated to use ECPublicKey and new RSA verify API
src/js/extensions/ccf/crypto.cpp	Updated to use make_ec_public_key and unified JWK methods
doc/build_apps/crypto.rst	Updated documentation to reflect new type names
CHANGELOG.md	Added entry documenting the breaking API changes