qemu-img: Use BlockNodeInfo

qemu-img: Use BlockNodeInfo

qemu-img info never uses ImageInfo's backing-image field, because it
opens the backing chain one by one with BDRV_O_NO_BACKING, and prints
all backing chain nodes' information consecutively.  Use BlockNodeInfo
to make it clear that we only print information about a single node, and
that we are not using the backing-image field.

Notably, bdrv_image_info_dump() does not evaluate the backing-image
field, so we can easily make it take a BlockNodeInfo pointer (and
consequentially rename it to bdrv_node_info_dump()).  It makes more
sense this way, because again, the interface now makes it syntactically
clear that backing-image is ignored by this function.

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220620162704.80987-6-hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>