admin: generate list of SHA-256 fingerprints for an incident table

[Preston12321]

The admin tool should be able to generate a list of SHA-256 fingerprints over the certificates described in an incident table.

This would be particularly useful for compliance incidents, because we usually need to provide a list of crt.sh or Censys links describing the entire corpus of affected certificates, which are best constructed using the SHA-256 hash.

[aarongable]

Based on the current proposed update to the incident reporting guidelines and template, we're going to need the admin tool to generate a lot more than just the sha256:

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In the case of incidents that directly impact certificates, the Appendix MUST include a comma separated listing of certificate details of all affected certificates and include the following fields for each:

Field	Description
Pre-certificate SHA-256 hash	A SHA-256 hash of the DER encoded pre-certificate.
Certificate SHA-256 hash	A SHA-256 hash of the DER encoded certificate.
Subject	The Subject field of the Certificate.
Issuer	The Issuer field of the Certificate.
Not before	The notBefore field of the Certificate.
Not after	The notAfter field of the Certificate.
Serial #	The Serial Number field of the Certificate, in hex.
Is revoked?	"Yes", "Planned","Delayed", or "N/A" (for expired)
Revocation date	Actual Date, Planned Date, or "N/A"
Revocation reason	The reasonCode corresponding with the Certificate's entry on the CRL.