Merge pull request #8469 from jtattermusch/csharp_perf_tuning

Run C# QpsWorker on all cores

src/csharp/Grpc.IntegrationTesting/QpsWorker.cs

@@ -76,6 +76,11 @@ namespace Grpc.IntegrationTesting
 
         private async Task RunAsync()
         {
+            // (ThreadPoolSize == ProcessorCount) gives best throughput in benchmarks
+            // and doesn't seem to harm performance even when server and client
+            // are running on the same machine.
+            GrpcEnvironment.SetThreadPoolSize(Environment.ProcessorCount);
+
             string host = "0.0.0.0";
             int port = options.DriverPort;