Fix Flaky Tests in GraphSONTypedCompatibilityTest

We observed several tests in GraphSONTypedCompatibilityTest  that exhibited flaky behavior when executed with NonDex. Specifically speaking, we can reproduce them by using the following commands.
```
mvn clean install -DskipTests -Drat.skip=true
```
* Test shouldReadWriteEdge[expect(v2)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteEdge[expect(v2)]" -Drat.skip=true
```

* Test shouldReadWriteEdge[expect(v3)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteEdge[expect(v3)]" -Drat.skip=true
```

* Test shouldReadWritePath[expect(v2)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWritePath[expect(v2)]" -Drat.skip=true
```

* Test shouldReadWritePath[expect(v3)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWritePath[expect(v3)]" -Drat.skip=true
```

* Test shouldReadWriteProperty[expect(v2)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteProperty[expect(v2)]" -Drat.skip=true
```

* Test shouldReadWriteProperty[expect(v3)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteProperty[expect(v3)]" -Drat.skip=true
```

* Test shouldReadWriteTraverser[expect(v2)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteTraverser[expect(v2)]" -Drat.skip=true
```

* Test shouldReadWriteTraverser[expect(v3)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteTraverser[expect(v3)]" -Drat.skip=true
```

* Test shouldReadWriteVertexProperty[expect(v2)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteVertexProperty[expect(v2)]" -Drat.skip=true
```

* Test shouldReadWriteVertexProperty[expect(v3)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteVertexProperty[expect(v3)]" -Drat.skip=true
```

* Test shouldReadWriteVertex[expect(v2)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteVertex[expect(v2)]" -Drat.skip=true
```

* Test shouldReadWriteVertex[expect(v3)]
```bash
mvn clean -pl gremlin-util edu.illinois:nondex-maven-plugin:2.2.1:nondex -Dtest="org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONTypedCompatibilityTest#shouldReadWriteVertex[expect(v3)]" -Drat.skip=true
```
And the error should be something like this:
```
[ERROR] Failures:
[ERROR]   GraphSONTypedCompatibilityTest>AbstractTypedCompatibilityTest.shouldReadWriteEdge:322 expected:<e[17][7-develops->10]> but was:<e[13][1-develops->10]>
[ERROR]   GraphSONTypedCompatibilityTest>AbstractTypedCompatibilityTest.shouldReadWriteEdge:322 expected:<e[17][7-develops->10]> but was:<e[13][1-develops->10]>
```

Upon our investigation, the root cause is the use of:
```
protected Map<Object, Vertex> vertices = new ConcurrentHashMap<>();
protected Map<Object, Edge> edges = new ConcurrentHashMap<>();
```
in TinkerGraph.java, which does not guarantee a deterministic order.

The simplest fix would be to replace ConcurrentHashMap with LinkedHashMap, as we did in a previous PR. We've confirmed that this change could remove the flakiness of these tests. However, we are concerned that such a change might introduce unintended side effects in the code under test. Another possible fix would be to deterministically select a fixed id, but that approach would make the test become sensitive to future implementation changes. Thus, we decided to use this sorting-based approach to deflake this test.

Author: KangweiZhu

gremlin-util/src/test/java/org/apache/tinkerpop/gremlin/structure/io/Model.java

@@ -40,6 +40,7 @@
 import org.apache.tinkerpop.gremlin.structure.VertexProperty;
 import org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerFactory;
 import org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerGraph;
+import org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils;
 import org.apache.tinkerpop.gremlin.util.message.RequestMessage;
 import org.apache.tinkerpop.gremlin.util.message.ResponseMessage;
 
@@ -115,12 +116,22 @@ private Model() {
         addCoreEntry(new java.sql.Timestamp(1481750076295L), "Timestamp", "");
         addCoreEntry(UUID.fromString("41d2e28a-20a4-4ab0-b379-d810dede3786"), "UUID");
 
-        addGraphStructureEntry(graph.edges().next(), "Edge", "");
-        addGraphStructureEntry(g.V().out().out().path().next(), "Path", "");
-        addGraphStructureEntry(graph.edges().next().properties().next(), "Property", "");
+        addGraphStructureEntry(IteratorUtils.list(graph.edges()).stream()
+                .sorted((e1, e2) -> Integer.compare((Integer)e1.id(), (Integer)e2.id()))
+                .iterator().next(), "Edge", "");
+        addGraphStructureEntry(g.V().order().by(T.id).out().out().path().next(), "Path", "");
+        addGraphStructureEntry(IteratorUtils.list(graph.edges()).stream()
+                .sorted((e1, e2) -> Integer.compare((Integer)e1.id(), (Integer)e2.id()))
+                .iterator().next().properties().next(), "Property", "");
         addGraphStructureEntry(graph, "TinkerGraph", "`TinkerGraph` has a custom serializer that is registered as part of the `TinkerIoRegistry`.");
-        addGraphStructureEntry(graph.vertices().next(), "Vertex", "");
-        addGraphStructureEntry(graph.vertices().next().properties().next(), "VertexProperty", "");
+        addGraphStructureEntry(IteratorUtils.list(graph.vertices()).stream()
+                .sorted((v1, v2) -> Integer.compare((Integer)v1.id(), (Integer)v2.id()))
+                .iterator().next(), "Vertex", "");
+        addGraphStructureEntry(IteratorUtils.list(IteratorUtils.list(graph.vertices()).stream()
+                .sorted((v1, v2) -> Integer.compare((Integer)v1.id(), (Integer)v2.id()))
+                .iterator().next().properties()).stream()
+                .sorted((p1, p2) -> Long.compare((Long)p1.id(), (Long)p2.id()))
+                .iterator().next(), "VertexProperty", "");
 
         addGraphProcessEntry(SackFunctions.Barrier.normSack, "Barrier", "");
         addGraphProcessEntry(new Bytecode.Binding("x", 1), "Binding", "A \"Binding\" refers to a `Bytecode.Binding`.");
@@ -153,7 +164,7 @@ private Model() {
         // TextP was only added at 3.4.0 and is not supported with untyped GraphSON of any sort
         addGraphProcessEntry(TextP.containing("ark"), "TextP", "");
         addGraphProcessEntry(createStaticTraversalMetrics(), "TraversalMetrics", "");
-        addGraphProcessEntry(g.V().hasLabel("person").asAdmin().nextTraverser(), "Traverser", "");
+        addGraphProcessEntry(g.V().hasLabel("person").order().by(T.id).asAdmin().nextTraverser(), "Traverser", "");
 
         final Map<String,Object> requestBindings = new HashMap<>();
         requestBindings.put("x", 1);