chore: add liveliness and readiness probes for nodes

## Overview
Due to bugs #172, it makes sense to add proper liveliness checks for all the nodes that are run.

## Implementation
Containers to add to:
* Validator container: run `status` cmd or rest call to `/status` endpoint
* exposer container
* registry container

> Note: Need to run smoke tests against the system to make sure there is no regression in performance of the repo