Merge changes I1625d1a6,I2db9cfa2,I59c31318,Ic0ed1a8d,I612374bb into main

* changes:
  snapuserd: Move Process ops out of Worker.
  snapuserd: Move more fields out of Worker.
  snapuserd: Split more methods out of Worker.
  snapuserd: Create a ReadWorker class.
  snapuserd: Create a MergeWorker class.