(PE-4308) API support for certificate_status endpoint

The first commit is for revoking certs, the second is for calculating the fingerprints of certs/csrs that are in the cert_status response, and the third is simply a convenience function for getting the subject DNS alt names from a cert/csr.

As I mentioned in standup, I broke the CRL API to no longer take a list of extensions - those will be added automatically now.
I tried but it's so ugly since there's no boolean? predicate I would need to do `(or (true? %) (false? %))` (or worse) and we don't have schema in this library to make it better.  Plus, we've fumbled around with trying to declare boolean pre/post conditions in previous PRs and we ended up not doing it, and in some cases just coerced the input rather than declare it must be `true` or `false`.

I figured it was okay to leave it off since it's obviously a predicate function, but I don't care too much either way.