SELinux type for vendor public libs.

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