Make X509_set_sm2_id consistent with other setters

This commit makes the X509_set_sm2_id to 'set0' behaviour, which means
the memory management is passed to X509 and user doesn't need to free
the sm2_id parameter later. API name also changes to X509_set0_sm2_id.

Document and test case are also updated.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8626)