Address high-cardinality attributes server.address and server.port attack vector

[trask]

As pointed out in by @joaopgrassi and team in #17 (comment).

The metric attributes server.address and server.port on the http.server.* metrics can be manipulated externally by spoofing the HTTP Host header, which can lead to similar cardinality problems and degraded observability as open-telemetry/opentelemetry-specification#3470 (http.request.method).

After discussing with @lmolkova, our recommendation is make server.address and server.port Opt-In on all http.server.* metrics.

We believe that the majority of instrumented apps do not expose multiple virtual hosts/ports, and that the service.name resource attribute is a reasonable alternative to server.address and server.port in these cases.