DA: Report long-lived on chain states (local/global states, boxes)

## Summary

On editor requesting for named variables, the DA server should respond long-lived app states for editor front end rendering.

## Completion Criteria

* The DA can support long-lived app state changes (for local/global states, boxes) when stepping through TEAL program
* Support these DAP requests:
* VariablesRequest
* The above actions should work with VSCode a client