Moved c.a.i.u.Predicate[s] into legacy-test

These classes are only used by android.test classes that are
being removed. As their name suggests they should not be in the
Android API at all so it makes sense to remove them. Especially
as there is java.lang.function.Predicate available now.

It appears as though Predicate was only added in to the API
because it was used by a method in the API as the directory in
which it and Predicates live was not on the list of classes to
explicitly index. Moving it into legacy-test meant that they are
now being indexed explicitly which means that Predicates needs
to be hidden.

Keeps running the tests as part of the existing target.

At runtime apps targeted at the API version before these are
removed will have the legacy-test library automatically added
to their classpath so they should see no effect. Apps that
target a later API will have to include those classes from the
android.legacy.test.jar which will contain all the android.test
classes that depend on it as well.

Bug: 30188076
Test: make checkbuild
Change-Id: Ia8502ec77ac11f85e078d70b68df214a9435eee7
Merged-In: I6f6f5f16fe93bd80227a450c6254166632fc6813