Features:
+* /etc/veritytab: allow that the roothash column can be specified as fs path
+ including a path to an AF_UNIX path, similar to how we do things with the
+ keys of /etc/crypttab. That way people can store/provide the roothash
+ externally and provide to us on demand only.
+
* add high-level lockdown level for GPT dissection logic: e.g. an enum that can
be ANY (to mount anything), TRUSTED (to require that /usr is on signed
verity, but rest doesn't matter), LOCKEDDOWN (to require that everything is