Nima Prometheus support

[romain-grecourt]

Update Prometheus support in 4.x:

Do one of the following:

• Evaluate Prometheus as a potential Metrics backend, if relevant implement a provider, depends on Metrics API for Helidon that is server agnostic and does not use MicroProfile metrics #4868
• Convert PrometheusSupport from a reactive WebServer Service to a Nima HttpServer or HelidonFeatureSupport
• Remove PrometheusSupport