[WIP] Allow using `test` logs from all_log_list.json for SCTs, in non-prod environments

[mcpherrinm]

This was a quick idea, not complete. Just opening for early feedback and CI run right now.

Chrome's all_logs_list has test logs marked as such. It would be good to restrict them to non-production environments to prevent configuration mistakes. Those logs don't have a status ("Qualified"/"Usable", etc), so that shouldn't be checked.

It's only handling Issuance right now, and may not be quite the right configuration scheme.

I'm also considering that the entire subset logic might not be the right thing to do - Should this just validate that the list of logs are configured properly, and return an error if they aren't? If at startup/config validation time, that would probably be more robust to configuration mistakes without silent unexpected behaviour.

[aarongable]

I think I'd prefer a boolean "SubmitToTestLogs: true". And then only care about the value of that boolean and the status of the log when constructing the list of SCTLogs -- the sets of InfoLogs and FinalLogs can submit to whatever logs we list, regardless of state and test status.

[mcpherrinm]

I agree a "Submit to test logs" boolean is probably better. One thing about Google's log list schema is that they don't explicitly enumerate the set of log types, and recently added one ("monitoring_only") that we might want to submit to, so I wasn't eager to either accept all types or hardcode the current two