qemu-img: Change info key names for protocol nodes

qemu-img: Change info key names for protocol nodes

Currently, when querying a qcow2 image, qemu-img info reports something
like this:

image: test.qcow2
file format: qcow2
virtual size: 64 MiB (67108864 bytes)
disk size: 196 KiB
cluster_size: 65536
Format specific information:
    compat: 1.1
    compression type: zlib
    lazy refcounts: false
    refcount bits: 16
    corrupt: false
    extended l2: false
Child node '/file':
    image: test.qcow2
    file format: file
    virtual size: 192 KiB (197120 bytes)
    disk size: 196 KiB
    Format specific information:
        extent size hint: 1048576

Notably, the way the keys are named is specific for image files: The
filename is shown under "image", the BDS driver under "file format", and
the BDS length under "virtual size".  This does not make much sense for
nodes that are not actually supposed to be guest images, like the /file
child node shown above.

Give bdrv_node_info_dump() a @protocol parameter that gives a hint that
the respective node is probably just used for data storage and does not
necessarily present the data for a VM guest disk.  This renames the keys
so that with this patch, the output becomes:

image: test.qcow2
[...]
Child node '/file':
    filename: test.qcow2
    protocol type: file
    file length: 192 KiB (197120 bytes)
    disk size: 196 KiB
    Format specific information:
        extent size hint: 1048576

(Perhaps we should also rename "Format specific information", but I
could not come up with anything better that will not become problematic
if we guess wrong with the protocol "heuristic".)

This change affects iotest 302, which has protocol node information in
its reference output.

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220620162704.80987-13-hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>