We switched from implicit CRL sharding (based on date) to explicit CRL sharding (based on the CRLDP embedded in a certificate). All certificates that used implicit CRL sharding are now expired. We should remove the old code. In particular, sa.GetRevokedCerts can go away (in favor of sa.GetRevokedCertsByShard).

Original issue: #7094

Implementation PRs:

#7946
#7918
#7990