[json-node] Add extract() methods to assist filtering and mapping

[rbygrave]

    JsonArray phoneNumbers = ...;

    List<String> result =
      phoneNumbers.stream()
        .filter(n -> "home".equals(n.extract("type")))
        .map(n -> n.extract("number"))
        .collect(Collectors.toList());

extract() can take a dot notation path like person.name (so not JSONPath)

    var node = JsonObject.create()
      .add("person", JsonObject.create().add("name", "myName").add("type", "doo").add("active", true))
      .add("address", JsonObject.create().add("size", 42).add("junk", 99L).add("other", JsonObject.create().add("deep", "one")));

    JsonNode name = node.find("name");
    assertThat(name).isNull();

    JsonNode personName = node.find("person.name");
    assertThat(personName).isNotNull();
    assertThat(personName.text()).isEqualTo("myName");

    assertThat(node.extract("person.name")).isEqualTo("myName");
    assertThat(node.extract("person.active")).isEqualTo("true");
    assertThat(node.extract("person.active", false)).isEqualTo(true);
    assertThat(node.extract("person.missing", false)).isEqualTo(false);

    assertThat(node.extract("address.size", -1)).isEqualTo(42);

    assertThat(node.extract("address.other.deep")).isEqualTo("one");