[Internal] [Feature] Refactor to bulk-submit samples

[jessicarowell]

This would probably involve a separate module that runs only once, at the end (like a "summarize" module). It would concatenate all the individual sample submission.xml files and submit one batch.

Place an ❌ in a Box that Best Matches the Feature's Importance:

• [] 1 - Most important (absolutely integral and will not use codebase at all without it)
• [] 2-4 - Moderate (still using codebase for other functions but is serving as a blocker for future use-cases)
• [] 5 - Least important (would like to see but there are no stringent expectations nor urgency for current/future use-cases) 

Any Additional Context or Information? Has There Been Any Progress Made So Far Towards this Request? Any Helpful Resources to Reference? Screenshots or Links?

Will update with my implementation plan later.