Add log to SendAsync_SlowServerRespondsAfterDefaultReceiveTimeout_ThrowsHttpRequestException. (dotnet#100525)

Author: rzikm

src/libraries/System.Net.Http.WinHttpHandler/tests/FunctionalTests/WinHttpHandlerTest.cs

@@ -122,6 +122,7 @@ await LoopbackServer.CreateServerAsync(async (server, url) =>
                         await triggerRequestWait.Task;
                         var _ = await t;
                     });
+                    _output.WriteLine($"ex: {ex}");
                     Assert.IsType<IOException>(ex.InnerException);
                     Assert.NotNull(ex.InnerException.InnerException);
                     Assert.Contains("The operation timed out", ex.InnerException.InnerException.Message);