socks5: improve throughput

[pymq]

I added local benchmark for socks5 throughput with simnet and different bandwidth and latency pairs. Unfortunately, it's still flaky on my device, and I have no idea how to fix it. Nevertheless, this PR improves network utilization by 1.5-3x, as confirmed by my tests with a real network on a high latency connection between Europe and Asia.

It is possible to cut the TTFB in half by removing one RTT. However, a new protocol needs to be implemented, which will be done in a future MR.

Before:

+-----------------------------+---------+-----------------+------------+------------+-------------+---------+
|          SCENARIO           | LATENCY | BANDWIDTH LIMIT | THROUGHPUT | THROUGHPUT | UTILIZATION |  TTFB   |
|                             |         |                 |    AVG     | LAST 5 SEC |             |         |
+-----------------------------+---------+-----------------+------------+------------+-------------+---------+
| WARM-UP                     | 10ms    | 50 Mbps         | 25.04 Mbps | 25.42 Mbps | 50.08 %     | 43.8ms  |
| Fiber_100Mbps_1ms           | 1ms     | 100 Mbps        | 57.06 Mbps | 59.48 Mbps | 57.06 %     | 8.1ms   |
| LongDistFiber_100Mbps_200ms | 200ms   | 100 Mbps        | 25.43 Mbps | 28.77 Mbps | 25.43 %     | 807.3ms |
| Cable_50Mbps_10ms           | 10ms    | 50 Mbps         | 26.73 Mbps | 26.57 Mbps | 53.45 %     | 44.6ms  |
| LongDistCable_50Mbps_300ms  | 300ms   | 50 Mbps         | 11.80 Mbps | 12.40 Mbps | 23.61 %     | 1.2058s |
| Cable_10Mbps_100ms          | 100ms   | 10 Mbps         | 8.18 Mbps  | 7.67 Mbps  | 81.80 %     | 404.1ms |
| LongDistCable_10Mbps_300ms  | 300ms   | 10 Mbps         | 6.68 Mbps  | 7.53 Mbps  | 66.79 %     | 1.207s  |
+-----------------------------+---------+-----------------+------------+------------+-------------+---------+

After:

+-----------------------------+---------+-----------------+------------+------------+-------------+---------+
|          SCENARIO           | LATENCY | BANDWIDTH LIMIT | THROUGHPUT | THROUGHPUT | UTILIZATION |  TTFB   |
|                             |         |                 |    AVG     | LAST 5 SEC |             |         |
+-----------------------------+---------+-----------------+------------+------------+-------------+---------+
| WARM-UP                     | 10ms    | 50 Mbps         | 26.03 Mbps | 26.28 Mbps | 52.05 %     | 47.2ms  |
| Fiber_100Mbps_1ms           | 1ms     | 100 Mbps        | 97.19 Mbps | 97.02 Mbps | 97.19 %     | 5.8ms   |
| LongDistFiber_100Mbps_200ms | 200ms   | 100 Mbps        | 59.54 Mbps | 67.28 Mbps | 59.54 %     | 802.5ms |
| Cable_50Mbps_10ms           | 10ms    | 50 Mbps         | 48.26 Mbps | 48.28 Mbps | 96.53 %     | 41.8ms  |
| LongDistCable_50Mbps_300ms  | 300ms   | 50 Mbps         | 29.42 Mbps | 37.10 Mbps | 58.85 %     | 1.202s  |
| Cable_10Mbps_100ms          | 100ms   | 10 Mbps         | 8.47 Mbps  | 8.70 Mbps  | 84.67 %     | 401.9ms |
| LongDistCable_10Mbps_300ms  | 300ms   | 10 Mbps         | 6.65 Mbps  | 7.61 Mbps  | 66.54 %     | 1.2019s |
+-----------------------------+---------+-----------------+------------+------------+-------------+---------+

(flaky)
+-----------------------------+---------+-----------------+------------+------------+-------------+---------+
|          SCENARIO           | LATENCY | BANDWIDTH LIMIT | THROUGHPUT | THROUGHPUT | UTILIZATION |  TTFB   |
|                             |         |                 |    AVG     | LAST 5 SEC |             |         |
+-----------------------------+---------+-----------------+------------+------------+-------------+---------+
| WARM-UP                     | 10ms    | 50 Mbps         | 25.27 Mbps | 25.56 Mbps | 50.55 %     | 48.1ms  |
| Fiber_100Mbps_1ms           | 1ms     | 100 Mbps        | 54.95 Mbps | 55.14 Mbps | 54.95 %     | 9.4ms   |
| LongDistFiber_100Mbps_200ms | 200ms   | 100 Mbps        | 24.46 Mbps | 27.76 Mbps | 24.46 %     | 806.8ms |
| Cable_50Mbps_10ms           | 10ms    | 50 Mbps         | 25.86 Mbps | 25.67 Mbps | 51.71 %     | 45.1ms  |
| LongDistCable_50Mbps_300ms  | 300ms   | 50 Mbps         | 10.69 Mbps | 12.19 Mbps | 21.37 %     | 1.2083s |
| Cable_10Mbps_100ms          | 100ms   | 10 Mbps         | 8.54 Mbps  | 8.99 Mbps  | 85.40 %     | 405.4ms |
| LongDistCable_10Mbps_300ms  | 300ms   | 10 Mbps         | 6.62 Mbps  | 7.51 Mbps  | 66.15 %     | 1.2064s |
+-----------------------------+---------+-----------------+------------+------------+-------------+---------+