Add Sample artifact type

[rshipp]

Add a new Sample artifact type to hold links to downloadable samples from app.any.run, hybrid-analysis, etc.

• [ ] Add Sample artifact class
  • [ ] Extend from URL class
  • [ ] Fields: atrifact will be the original extracted url
  • [ ] Str method: modify the original url as needed to produce direct download URL
• [ ] Extract Sample artifacts in sources.process_element
  • [ ] Include only nonobfuscated urls from the sample domain whitelist
• [ ] Add support for new artifact to SQS and CSV operators

[rshipp]

Note: this was implemented differently than described.