Provide better probes for rendition micro services

During the investigation of NEV-381, we noticed that a JNI/document-renderer crash provokes a broker crash. We also noticed this behavior when the PDFBOX/document-text-handler restarts.

The broker shouldn't be impacted by the other microservices restarts.
This is due to the liveness probe which checks the /weather path. This endpoint returns the full stack health, thus the broker restarts when a microservice restart.

This ticket aims to provide endpoints respecting the Kubernetes definition for each rendition microservices.
We're gonna focus on liveness and readiness probes for now as startup probe is available since Kubernetes 1.20. But it could be interesting to dig a bit into it in order to leverage this new feature once we're gonna have a compatible cluster.