Add support for printing SCTs

[jdtw]

Fixes https://github.com/square/certigo/issues/171

Example from certigo connect -v google.com:

Signed Certificate Timestamp:
    Version: 0 (v1)
    Log Operator: Google
    Log URL: https://ct.googleapis.com/logs/xenon2022/
    Log ID: 46:A5:55:EB:75:FA:91:20:30:B5:A2:89:69:F4:F3:7D:
            11:2C:41:74:BE:FD:49:B8:85:AB:F2:FC:70:FE:6D:47
    Timestamp: 2022-06-06 02:29 PDT
    Signature: ECDSA-SHA256
Signed Certificate Timestamp:
    Version: 0 (v1)
    Log Operator: DigiCert
    Log URL: https://nessie2022.ct.digicert.com/log/
    Log ID: 51:A3:B0:F5:FD:01:79:9C:56:6D:B8:37:78:8F:0C:A4:
            7A:CC:1B:27:CB:F7:9E:88:42:9A:0D:FE:D4:8B:05:E5
    Timestamp: 2022-06-06 02:29 PDT
    Signature: ECDSA-SHA256

We keep a hard-coded list of known logs that can be updated by running make ctlogs from the repo root.