Umbrella issue -- parallelism improvements

[elijahbenizzy]

All the improvements to parallelism that we want to make post the first release:

• [ ] UI improvements
  • [x] Expand parallel apps inline (#421)
    • [x] Show success/failure
  • [ ] Ensure insights tab shows aggregation of all parallel sub-applications
  • [ ] Show the sub-applications graphs in the graph
  • [x] Ensure live mode works (#421)
  • [x] Ensure the hierarchy of traces is clear (#421)
• [ ] Task creation/management
  • [ ] Add API for task IDs
    • [ ] Add API
    • [ ] Wire through to UI
    • [ ] Add documentation
• [ ] Guard-rails around async problems
  • [ ] Ensure that generators that are both async and not async work as expected
• [x] Wiring through persisters
  • [x] Allow wiring through of persisters to sub-trackers
    • [x] Implement this spec: https://burr.dagworks.io/concepts/parallelism/#persistence-tracking -- not currently doable
• [ ] Execution improvements
  • [ ] Reevaluate execution API
  • [ ] Add guard-rails for executors (E.G. with async, etc...)
  • [ ] Allow customization of execution capabilities on a per-task basis
• [x] Ensure recursion works -- multiple levels deep