Add support for 'image' volume driver

We added the concept of image volumes in 2.2.0, to support
inspecting an image from within a container. However, this is a
strictly read-only mount, with no modification allowed.

By contrast, the new `image` volume driver creates a c/storage
container as its underlying storage, so we have a read/write
layer. This, in and of itself, is not especially interesting, but
what it will enable in the future is. If we add a new command to
allow these image volumes to be committed, we can now distribute
volumes - and changes to them - via a standard OCI image registry
(which is rather new and quite exciting).

Future work in this area:
- Add support for `podman volume push` (commit volume changes and
  push resulting image to OCI registry).
- Add support for `podman volume pull` (currently, we require
  that the image a volume is created from be already pulled; it
  would be simpler if we had a dedicated command that did the
  pull and made a volume from it)
- Add support for scratch images (make an empty image on demand
  to use as the base of the volume)
- Add UOR support to `podman volume push` and
  `podman volume pull` to enable both with non-image volume
  drivers

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

libpod/volume_inspect.go

@@ -64,6 +64,7 @@ func (v *Volume) Inspect() (*define.InspectVolumeData, error) {
 	data.MountCount = v.state.MountCount
 	data.NeedsCopyUp = v.state.NeedsCopyUp
 	data.NeedsChown = v.state.NeedsChown
+	data.StorageID = v.config.StorageID
 
 	if v.config.Timeout != nil {
 		data.Timeout = *v.config.Timeout