Document how to deploy Hono without optional Prometheus support

[JouHouFin]

Eclipse Hono has built-in support for Prometheus monitoring: https://www.eclipse.org/hono/docs/admin-guide/monitoring-tracing-config/#using-prometheus

Investigate if it is possible (and useful) to enable the Prometheus support only if needed.

Document what needs to be done if someone wants to use deployment scripts to deploy just Hono without Prometheus.

[hjhsalo]

Note that if Prometheus deployment is done outside of Hono Helm charts, Terraform code changes are needed to disable both Prometheus support for Hono microservices and to disable whole deployment of Prometheus.