Extract `net.peer.{name,port}` on start for CLIENT spans (#6828)
The [HTTP
spec](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-client)
says these two attributes must be provided at span creation time - I
think it makes sense to extend it over to all `net`-related
instrumentations, cause these are supposed to be the logical peer
name/port, which are supposed to be known before the connection is
started/exchange is made.
77035fc88c