Refactor `AbstractSimpleTransportTestCase` and `MockTransportService` to not use `Version.transportVersion` 
test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java
final int value2;
        Version1Response(int value1, int value2) {
            super(value1);
            this.value2 = value2;
        }
        Version1Response(StreamInput in) throws IOException {
            super(in);
            if (in.getTransportVersion().onOrAfter(version1.transportVersion)) {
                value2 = in.readInt();
            } else {
                value2 = 0;
            }
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            super.writeTo(out);
            if (out.getTransportVersion().onOrAfter(version1.transportVersion)) {
                out.writeInt(value2);