virt-aa-helper: add rules for shmem devices

virt-aa-helper: add rules for shmem devices

Shared memory devices need qemu to be able to access certain paths
either for the shared memory directly (mostly ivshmem-plain) or for a
socket (mostly ivshmem-doorbell).

Add logic to virt-aa-helper to render those apparmor rules based
on the domain configuration.

https://bugzilla.redhat.com/show_bug.cgi?id=1761645

Reviewed-by: Cole Robinson <crobinso@redhat.com>
Acked-by: Jamie Strandboge <jamie@canonical.com>
Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>