Readiness and liveliness probes on logging sidecar

If and when fluent bit is integrated into server or the sidecar becomes non-optional we should enable the healthcheck probes (easiest way is via the :2020 web server and that's how the helm chart does it).

We would have to consider the implications on preventing Couchbase from running if the sidecar is not working or has an invalid configuration - but some customers may be relying on it for logging (e.g. audit) as well. A custom configuration could also disable the web server and therefore the probes.

With the 1.8 series now of Fluent Bit we have a simple health check included: https://docs.fluentbit.io/manual/administration/monitoring#health-check-for-fluent-bit