Use X509_get_signature_info() when checking security levels.

Make signature security level checking more flexible by using
X509_get_signaure_info(): some signature methods (e.g. PSS, ED25519)
do not indicate the signing digest (if any) in the signature OID.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3301)