Select choice filters should be as fast as other XPath predicates

[seadowg]

The same complexity profiles that we ended up with for getodk/javarosa#689 should apply for selects with choice filters.

An example test that shows this is not the case is:

Scenario scenario = Scenario.init("Some form", html(
    head(
        title("Some form"),
        model(
            mainInstance(t("data id=\"some-form\"",
                t("choice"),
                t("select")
            )),
            instance("instance",
                item("a", "A"),
                item("b", "B")
            ),
            bind("/data/choice").type("string"),
            bind("/data/select").type("string")
        )
    ),
    body(
        input("/data/choice"),
        select1Dynamic("/data/select", "instance('instance')/root/item[value = /data/choice]")
    )
));

int evaluations = Measure.withMeasure(asList("PredicateEvaluation", "IndexEvaluation"), () -> {
    scenario.answer("/data/choice", "a");
    scenario.choicesOf("/data/select");

    scenario.answer("/data/choice", "b");
    scenario.choicesOf("/data/select");
});

// Check that we do less than (size of secondary instance) * (number of choice lookups)
assertThat(evaluations, lessThan(4));