Fix the encoding of SM2 keys

Fix the encoding of SM2 keys

OpenSSL's encoding of SM2 keys used the SM2 OID for the algorithm OID
where an AlgorithmIdentifier is encoded (for encoding into the structures
PrivateKeyInfo and SubjectPublicKeyInfo).

Such keys should be encoded as ECC keys.

Fixes #22184

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22529)

(cherry picked from commit 1d490694dfa790d8e47f8f2ea62ea1d9b1251179)