Reland "Add more methods to opaque guest state"

This relands commit 4bd0e7c04b75da63400cd75270632264393e6d99.

Add more methods to opaque guest state

Adds more methods to guest_state_opaque so more code can be guest-arch
agnostic.

Change-Id: I33950ee95336c5d99b2d3f69ddb655842ea7c37d
Test: mm && berberis_host_tests
Bug: 283298171
6 files changed