Get rid of io.scalecube.services.gateway.GatewayMetrics

[artem-v]

• Dependency on codahale: Prod code must not include codahale.

  import com.codahale.metrics.Counter;
  import com.codahale.metrics.Meter;

• Naive implementation: All followign metrics could be provided without compiling into prod code.

  private final Counter connectionCounter;
  private final Meter requestMeter;
  private final Meter responseMeter;
  private final Meter serviceResponseMeter;

[artem-v]

Done it. Closing.