Clean up Predicate related code in android.test

Part of the work of removing JUnit and dependent android.test classes
from the Android API involves providing a static library that developers
can include in their test applications to ease migration. That library
will be built directly from the source (as opposed to android.jar which
is built from stubs) and so developers will be able to see classes and
methods that are not present in the stubs. This change is one of a
number of similar changes that cleanup the existing non-API code in
order to minimize the additional methods and classes exposed externally.
The basic approach is to remove unused classes and methods, use least
visible access modifier possible and generally minimize the amount of
publicly visible code.

The HasClassAnnotation and HasMethodAnnotation were never used
separately and only used by HasAnnotation. This merges the functionality
into a single nested class in TestPredicates, hidden behind the new
TestPredicates.hasAnnotation(). The HasAnnotationTest was renamed as
TestPredicatesTest and the HasClassAnnotationTest and
HasMethodAnnotationTest classes were removed as their tests provide no
additional coverage. The removal of the Has*Annotation.java files means
that the test-runner/src/android/test/suitebuilder/annotation/ directory
is empty apart from the package.html file so that was moved to
legacy-test to sit alongside the actual annotation classes.

The Predicates class, while part of the legacy-test module was only
ever used by the test-runner module and only its not() method was
actually used. So, the not() method and associated nested class were
moved to TestPredicates, the tests for not() were moved to
TestPredicatesTest and the Predicates* classes were removed.
That allowed for the removal of the legacy-android-tests as that is now
empty.

TestPredicates has a number of constants that were public. They were
hidden by moving them to the class that actually used them.

A minor generic issue was fixed in AssignableFrom.

Bug: 30188076
Test: make checkbuild and run FrameworkTestRunnerTests
Change-Id: I861da388a4146bb28e1e480d1b7ba9137b7b270e