[Internal] Distributed Tracing: Fixes Client Config Test (#4406)

* Adds code to create activity even customer is not subscribed to the feature

* Added documentation

Microsoft.Azure.Cosmos/src/Telemetry/OpenTelemetry/OpenTelemetryRecorderFactory.cs

@@ -69,6 +69,7 @@ public static OpenTelemetryCoreRecorder CreateRecorder(string operationName,
  // Safety check as diagnostic logs should not break the code.
  if (Activity.Current?.TraceId != null)
  {
+ // This id would be useful to trace calls at backend services when distributed tracing feature is available there.
  trace.AddDatum("DistributedTraceId", Activity.Current.TraceId);
  }
  }