block/rbd: Add support for layered encryption

block/rbd: Add support for layered encryption

Starting from ceph Reef, RBD has built-in support for layered encryption,
where each ancestor image (in a cloned image setting) can be possibly
encrypted using a unique passphrase.

A new function, rbd_encryption_load2, was added to librbd API.
This new function supports an array of passphrases (via "spec" structs).

This commit extends the qemu rbd driver API to use this new librbd API,
in order to support this new layered encryption feature.

Signed-off-by: Or Ozeri <oro@il.ibm.com>
Message-Id: <20230129113120.722708-4-oro@oro.sl.cloud9.ibm.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>