Fix and beautify OCTET STRING class hierarchy

[JesusMcCloud]

enables processing as such:

val TbsCertificationRequest.attestationProof: List<ByteArray>?
    get() = runCatching {
        attributes?.find { it.oid == OID_ATTESTATION_PROOF }?.value?.singleOrNull()
            .let { it as Asn1Sequence }.children.map { (it as Asn1OctetString<*>).content }
    }.getOrNull()

[nodh]

nice!

[JesusMcCloud]

it's already in development