[Sarkoxed]

Makes the TBS public-key extraction bind to the DER structure of SubjectPublicKeyInfo rather than to fixed byte offsets, so it parses the encoding diversity present in real Document Signer Certificates.

• RSA: anchor on the 11-byte rsaEncryption OID element, then skip an optional NULL before the BIT STRING.
• EC: skip exactly one element after the algorithm OID, accepting both namedCurve (tag 06) and explicit params (tag 30).
• Length decoding via utils::read_der_length

[saleel]

Can also remove long comments where not absolutely requried