Jetty metrics configuration option

[marsmining]

The HTTP component could support a configuration option for enabling "free" Jetty metrics from instrumented implementations of key interfaces via metrics-jetty9. An example configuration.

[lasomethingsomething]

Hi @marsmining, looks like you didn't get a response. Adding @dryewo for his thoughts. If he's supportive of the idea, would you be willing to make a PR?

[dryewo]

Brandon, please go on and make a PR. It looks like a nice feature.