[HardMax71]

Fixes #1229

ECAlgorithm.prepare_key and OKPAlgorithm.prepare_key let cryptography's ValueError (or UnsupportedAlgorithm) through when a PEM or SSH key can't be parsed. RSAAlgorithm raises InvalidKeyError for the same input since #952, so code that catches PyJWTError around decode() only breaks for EC and Ed25519 keys.

• EC: wrap the fallback load_pem_private_key, the same way RSA wraps its fallback.
• OKP: wrap the decode and the three loaders. Non-UTF-8 bytes raise UnicodeDecodeError, which is a ValueError too, so that case is covered as well.
• check_crypto_key_type: join the class names, so the message reads Expected one of EllipticCurvePrivateKey, EllipticCurvePublicKey, got: RSAPublicKey instead of printing a generator object.

Both new errors say "Could not parse the provided key." because EC and OKP try both public and private keys.

Tests: parametrized cases for EC (3 inputs) and OKP (4 inputs), plus a match on the existing EC wrong-key test for the message. All of them fail on master. The full suite passes with and without cryptography, and mypy and the pre-commit hooks pass. Changelog entry added under Unreleased.

#1199 also rewrites OKPAlgorithm.prepare_key, so whichever lands second needs a small rebase there.

[HardMax71]

@jpadilla could you review this when you have time? It raises InvalidKeyError for EC and OKP keys that can't be parsed.