fix: add missing minio_s3_requests_total (#15070)

PR #15052 caused a regression, add the missing metrics back.

Bonus:

- internode information should be only for distributed setups 
- update the dashboard to include 4xx and 5xx error panels.

cmd/http-stats.go

@@ -199,6 +199,8 @@ func (st *HTTPStats) updateStats(api string, r *http.Request, w *logger.Response
 		return
 	}
 
+	st.totalS3Requests.Inc(api)
+
 	// Increment the prometheus http request response histogram with appropriate label
 	httpRequestsDuration.With(prometheus.Labels{"api": api}).Observe(w.TimeToFirstByte.Seconds())