Add missing tests for queries

Some queries are not covered by our test suite. Here are a couple of examples. Note that all examples operate on Modern graph.

1. g.V().properties("age").order().by(T.id)

2. g.V().aggregate("a").has("person","age", P.gte(8)).cap("a").unfold().valueMap()
3. g.V().hasLabel("person").as("foo").where(__.outE("knows").count().is(P.gte(0))).select("foo")
4. g.V().properties().dedup()
5. g.V().project("id", "project").by(T.id).by(__.project("label").by(out().id().fold()).fold()
6. g.V().limit(3).addV("testLabel") .aggregate("a1").by(T.label) .aggregate("a2").by(T.label) .cap("a1", "a2");
7. g.V().as("a").path().by(T.id).as("path").project("a").by(identity())
8. g.V().group().by(label).count()