Add Akka.IO.Tcp benchmark

[IgorFedchenko]

To start work on issue #3328 we need to be able to measure Akka.IO.Tcp throughput before and after migration to System.IO.Pipelines and compare.

This PR adds benchmark as a simple client-server communication, exchanging with different number of messages with different payload sizes.

[IgorFedchenko]

I am making 100 iterations per parameters combination, and two values per parameter. As you can see increasing message count gives linear increase of time consumed (I have also tried bigger values), and payload almost does not change time (which is pretty understandable in localhost networking).

Here is what I am getting on my local machine right now:

                    Method | MessageCount | MessageLength |      Mean |     Error |    StdDev |    Median | Allocated |
-------------------------- |------------- |-------------- |----------:|----------:|----------:|----------:|----------:|
 ClientServerCommunication |          100 |            10 |  42.54 ms | 2.7769 ms |  8.188 ms |  40.55 ms |       0 B |
 ClientServerCommunication |          100 |           100 |  40.98 ms | 0.6515 ms |  1.921 ms |  40.31 ms |       0 B |
 ClientServerCommunication |         1000 |            10 | 388.77 ms | 8.4383 ms | 24.881 ms | 380.52 ms |       0 B |
 ClientServerCommunication |         1000 |           100 | 377.30 ms | 3.9668 ms | 11.696 ms | 373.36 ms |       0 B |

[Aaronontheweb]

So ~380ms for 1000 round trips?

[IgorFedchenko]

So ~380ms for 1000 round trips?

Yes