Create spans on new Netty connection

[iNikem]

Netty instrumentation ChannelFutureListenerInstrumentation creates a span with special name CONNECT when connection failed to open. As creating new connection may be potentially an expensive operation there is a client request to capture all cases of creating new connection as span. Ideally with correct, non-zero, duration. This also will help exposing problems when connection pool does not work as expected.