Add @Nullable and @NonNull to intra-core API

We want to annotate methods in the new files in external/conscrypt,
which can only depend on libcore via the intra-core API, so we need
access to these annotations.

Bug: 120475246
Test: make checkbuild
Change-Id: Ie7a7a59a84b2d86db1e9ef4499dd596c75f2bb17
4 files changed