Skip forced package verification if fs-verity exists

Unlike the original implementation, package can be verified with an
in-kernel trusted keyring.  In this case, we simply need to know if
fs-verity exists for the file.

Test: observed expected behavior with extra debug log
Bug: 112037636
Change-Id: I7a6ff35853f24f5a0a2727ddef376f9857a2d789