Fix OpenSSL object leaks on error paths in key conversion

[djw8605]

Problem

In the OpenSSL 3.x code paths of es256_from_coords(), rs256_from_coords(), and store_public_ec_key(), several objects were held as raw pointers and freed only on the success path:

• the EVP_PKEY produced by EVP_PKEY_fromdata,
• the OSSL_PARAM array from OSSL_PARAM_BLD_to_param / EVP_PKEY_todata,
• the buffer allocated by EC_POINT_point2buf.

Every intervening failure throws UnsupportedKeyException — parameter-build failure, EVP_PKEY_fromdata failure, PEM serialization failure, EC point conversion failure — and leaks whatever had been allocated up to that point. These paths are reachable with malformed JWKS content, so a hostile or buggy issuer can leak memory on every validation attempt.

Fix

Hold each object in a unique_ptr with the appropriate OpenSSL deleter (EVP_PKEY_free, OSSL_PARAM_free, OPENSSL_free), matching the RAII style already used for the surrounding objects (EC_GROUP, EC_POINT, OSSL_PARAM_BLD, BIGNUMs). No behavior change on the success path; OpenSSL 1.x paths untouched.

Testing

• ctest unit, env_config, and monitoring suites pass (the suites exercise both the ES256 and RS256 conversion paths via the keycache tests).

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