Feature request: request duration metrics for fetch & http requests

[omawhite]

It would be nice to add these metrics to the existing instrumentation to match the functionality provided by the @opentelemetry/instrumentation-http package, you can see where they're creating these metrics here.

I'm self hosting next.js and have my app connected to an opentelemetry collector, having these metrics be a part of this package would allow me to calculate things like HTTP request rate, latency, error rate, etc, in grafana.

I tried passing @opentelemetry/instrumentation-http in as an instrumentation to see if I could get it to work alongside the existing instrumentation provided by this package, but doing so resulted in my next.js spans missing attributes like http.route, next.route and other next specific span attributes.