qemu-img: map: report compressed data blocks

qemu-img: map: report compressed data blocks

Right now "qemu-img map" reports compressed blocks as containing data
but having no host offset.  This is not very informative.  Instead,
let's add another boolean field named "compressed" in case JSON output
mode is specified.  This is achieved by utilizing new allocation status
flag BDRV_BLOCK_COMPRESSED for bdrv_block_status().

Also update the expected qemu-iotests outputs to contain the new field.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Message-ID: <20230907210226.953821-3-andrey.drobyshev@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>