chore: improve sandbox code org #1657
Description
Background
The file vote.rs and common.rs have gotten unreasonably large. We can safely split them
User Story
As a dev, I like order
Acceptance Criteria
Move helper functions for sandbox tests into a separate crate.
Move unit tests into appropriately named files (i.e. one for resharing, one for key generation, one for tee, ...)
Resources & Additional Notes
No response