Support S3/etc output instead of disk-based output

[konklone]

It would be a very handy feature to drop data output to S3 instead of to disk. This would enable easy searching/indexing of output in something like Amazon Athena, while also requiring a lot less infrastructure/disk/constraints to run domain-scan itself.

Since the abstraction difference between S3 and disk is pretty slim, it would also be likely worth it to add in enough adapter-ish code to easily support being extended to other non-disk destinations, such as Google Cloud Storage.