feat(x509): add CRL type support

[npmccallum]

This contains just the CRL portion of #462. I made sure to give @carl-wallace the author's credit.

One remaining question I have is why these are in the crl module. Are these types used in extensions? Or are they disconnected data types? If the latter, crl is probably the best place for them.

@tarcieri FYI

[carl-wallace]

I don't know what you mean by "these". The definitions in crl.rs are associated with crl processing. I will close #462 and keep eye on this repo and align higher level bits as this catches up.

[npmccallum]

@carl-wallace I mean the types in the crl module in this PR. Are the crl types used in extensions?

[carl-wallace]

No. There are only three structures: the primary CRL structure, its TBS structure and a structure fabricated from the revoked certs field of the TBS structure (as noted in the comment, for some reason the spec authors defined this structure inline). Feel free to split into smaller pieces if you prefer. Credit should probably go to Alan Smithee:-)

[npmccallum]

@carl-wallace Who would use these types and how are they used?

[carl-wallace]

See the comments in the code. https://datatracker.ietf.org/doc/html/rfc5280#section-5.1

[npmccallum]

@carl-wallace The standard defines the data types and what is hopes they accomplish from the perspective of 2008. It doesn't describe how these types are actually used in 2022. I'm hoping you can fill me in on the common usage patterns.

[carl-wallace]

these are fundamental structures. where crls are used, these are in play.

[tarcieri]

Thanks!

@carl-wallace hopefully this works for your use cases, or if not, feel free to open a PR to make adjustments