add disk rename feature

add disk rename feature

Functionality has been added for the following storage types:

* directory ones, based on the default implementation:
    * directory
    * NFS
    * CIFS
    * gluster
* ZFS
* (thin) LVM
* Ceph

A new feature `rename` has been introduced to mark which storage
plugin supports the feature.

Version API and AGE have been bumped.

Signed-off-by: Aaron Lauterer <a.lauterer@proxmox.com>
the intention of this feature is to support the following use-cases:
- reassign a volume from one owning guest to another (which usually
  entails a rename, since the owning vmid is encoded in the volume name)
- rename a volume (e.g., to use a more meaningful name instead of the
  auto-assigned ...-disk-123)

only the former is implemented at the caller side in
qemu-server/pve-container for now, but since the lower-level feature is
basically the same for both, we can take advantage of the storage plugin
API bump now to get the building block for this future feature in place
already.

adapt ApiChangelog change to fix conflicts and added more detail above

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>