Populate the function x509_ocsp_get_cert_id() that parses the following
ASN.1 structure:
CertID ::= SEQUENCE {
hashAlgorithm AlgorithmIdentifier,
issuerNameHash OCTET STRING, -- Hash of issuer's DN
issuerKeyHash OCTET STRING, -- Hash of issuer's public key
serialNumber CertificateSerialNumber }
x509_ocsp_get_cert_id() parses the top-level SEQUENCE component and
calls the following helpers for the actual contents of the CertID:
* mbedtls_x509_get_md_alg(): Parses the hashAlgorithm
* x509_ocsp_get_octet_string(): Parses the OCTET STRINGs
issuerNameHash and issuerKeyHash, but does not actually check
that the length or hashes are actually correct or correspond
to the expected length given the hashAlgorithm
* mbedtls_x509_get_serial: Parses the serialNumber