Vendor public libs are exposed to apps (not system), and their ABI
stability is guaranteed by vendor. Introducing new selinux type so that
we don't conflate concepts of same-process HAL and vendor public lib.
The former is exposed to all domains, while the latter should only be
acessible by apps.

Bug: 76413554
Test: build-only change, policy builds
Change-Id: I89dad351374f46c7fe2726991eb4c05064c37ed5