Netty instrumentation

[felixbarny]

Netty is used as the foundation of a lot of client and server implementations. If we have generic support for monitoring HTTP requests, we'd already provide basic insight for lots of web frameworks.

One complication could be when Netty is used as the foundation of a Servlet container where we already instrument at the Servlet/Filter level.

That also doesn't solve context propagation for frameworks like Play which use Netty as the foundation but also have their own threading model.

relates to #722

[brento1]

Just curious, what is this currently being blocked by? @eyalkoren
We have started using micronaut as our microservice framework, and would love to have things autoconfigured with APM.

[eyalkoren]

@brentonr94 this is not blocked, it just didn't get to the top of our priorities yet, but it's definitely an item on our long-term roadmap.