Implement unit tests for vCard exporter, which depends on the sucess in vCard importer.

In order to share the logic between tests for importer and those for exporter,
PropertyNodesVerifier is now a separated class and drastically modified.
Now the class accept "unordered" expected PropertyNode objects, which allows vCard
composer to not care the exact order of each elements.

MockCursor is added, which may be added into the public API in the future, but in
the test directory for now.
Another MockContentProvider is (temporarily) developed so that it can be accepted by
MockContentResolver#addProvider(), which does not allow IContentProvider and its
descendants but only exact ContentProvider, while the original MockContentProvider in
android.test.mock.MockContentProvider implements IContentProvider.

The test development is still on-going, but this test suffices minimal requirement of
vCard tests.

Internal issue number: 2160039