Refactor `AbstractSimpleTransportTestCase` and `MockTransportService` to not use `Version.transportVersion` 
test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java
builder.addConnections(
            1,
            TransportRequestOptions.Type.BULK,
            TransportRequestOptions.Type.PING,
            TransportRequestOptions.Type.RECOVERY,
            TransportRequestOptions.Type.REG,
            TransportRequestOptions.Type.STATE
        );
        try (Transport.Connection connection = openConnection(serviceC, serviceB.getLocalNode(), builder.build())) {
            assertBusy(() -> { 
                TransportStats transportStats = serviceC.transport.getStats(); 
                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());