Refactor `AbstractSimpleTransportTestCase` and `MockTransportService` to not use `Version.transportVersion` 
test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java
assertEquals(1, transportStats.getRxCount());
                assertEquals(1, transportStats.getTxCount());
                assertEquals(29, transportStats.getRxSize().getBytes());
                assertEquals(55, transportStats.getTxSize().getBytes());
            });
            serviceC.sendRequest(
                connection,
                "internal:action",
                new TestRequest("hello world"),
                TransportRequestOptions.EMPTY,
                transportResponseHandler
            );
            receivedLatch.await();
            assertBusy(() -> { 
                TransportStats transportStats = serviceC.transport.getStats(); 
                assertEquals(1, transportStats.getRxCount());
                assertEquals(2, transportStats.getTxCount());
                assertEquals(29, transportStats.getRxSize().getBytes());
                assertEquals(114, transportStats.getTxSize().getBytes());
            });
            sendResponseLatch.countDown();
            responseLatch.await();
            stats = serviceC.transport.getStats(); 
            assertEquals(2, stats.getRxCount());
            assertEquals(2, stats.getTxCount());
            assertEquals(54, stats.getRxSize().getBytes());
            assertEquals(114, stats.getTxSize().getBytes());
        } finally {
            serviceC.close();
        }