Add Doclava support for federated APIs not referenced from code

Previously, @link and @see could only be used to reference APIs that were
also referenced from code. Since the platform cannot reference Support
Library APIs from code, this limitation prevented federation.

Federated APIs are now registered in the global Converter and TypeInfos
may now lazily resolve their classes.

Bug: 36959367
Test: make docs
Change-Id: Ie0c0672dbd8bfe2837ec60bc7c7e49cf67c43236
4 files changed