Support using different GSI keys for verification

The GSI images might be signed by any of the three GSI keys.
Allowing all of them for verification as they're all official
keys. With this, we don't have to require using VTS package
from a specific branch.

Bug: 149806657
Test: vts-tradefed run vts -m VtsSecurityAvb
Change-Id: I22aee50f0efb4bd38e49f2d1813e6128fb60b035
4 files changed