Request reply baseline benchmark (#453)

* Request reply benchmarks

* wip

* wip

* Revert experimental code

* Revert experimental code

* Revert MicroBenchmark project

* Simplified req-rep benchmark

* Check return value

sandbox/MicroBenchmark/RequestReplyBench.cs

@@ -0,0 +1,48 @@
+using BenchmarkDotNet.Attributes;
+using NATS.Client.Core;
+
+#pragma warning disable CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.
+
+namespace MicroBenchmark;
+
+[MemoryDiagnoser]
+[ShortRunJob]
+[PlainExporter]
+public class RequestReplyBench
+{
+    private NatsConnection _nats;
+    private CancellationTokenSource _cts;
+    private Task _subscription;
+
+    [GlobalSetup]
+    public async Task SetupAsync()
+    {
+        _nats = new NatsConnection();
+        await _nats.ConnectAsync();
+        _cts = new CancellationTokenSource();
+        _subscription = Task.Run(async () =>
+        {
+            await foreach (var msg in _nats.SubscribeAsync<int>("req_rep_bench", cancellationToken: _cts.Token))
+            {
+                await msg.ReplyAsync(0xBEEF);
+            }
+        });
+    }
+
+    [GlobalCleanup]
+    public async Task CleanupAsync()
+    {
+        await _cts.CancelAsync();
+        await _subscription;
+        await _nats.DisposeAsync();
+    }
+
+    [Benchmark]
+    public async Task<int> RequestReplyAsync()
+    {
+        var reply = await _nats.RequestAsync<int, int>("req_rep_bench", 0xDEAD);
+        var result = reply.Data;
+        ArgumentOutOfRangeException.ThrowIfNotEqual(0xBEEF, result);
+        return result;
+    }
+}