The CSI Spec requires us to attach and stage volumes based on different
types of usage information when it may effect how they are bound. Here
we pass through some basic usage options in the CSI Hook (specifically
the volume aliases ReadOnly field), and the attachment/access mode from
the volume. We pass the attachment/access mode seperately from the
volume as it simplifies some handling and doesn't necessarily force
every attachment to use the same mode should more be supported (I.e if
we let each `volume "foo" {}` specify an override in the future).