Desired properties of V4 format artifact file

[johngray-dev]

As per https://github.com/IETF-Hackathon/pqc-certificates/discussions/111 the next artifact version file should have the following properties

• Use only the latest OIDs so it is not encumbered by many of the older formats
• Use DER encoding so that PEM encoding issues get eliminated.

[johngray-dev]

• Discussion of adding private keys to the format in the June meeting. Especially with some cases with seeds and such.

[johngray-dev]

Specify the list of OIDS to be used in each artifact format.