rust: update der-parser to 8.2.0

rust: update der-parser to 8.2.0

Minimal modifications required on the Suricata side, mainly for fields
becoming private and needing an accessor instead.

Note: As the kerberos parser still depends on der-parser 6.0, we still
have to depend on that so it is depended on, but renamed to
der-parser6. There is not an udpated kerberos-parser yet that uses
der-parser 8.2.0.

Ticket: #5991