qemu-img info: Add cache mode option

qemu-img info: Add cache mode option

When querying block limits, different cache modes (in particular
O_DIRECT or not) can result in different limits. Add an option to
'qemu-img info' that allows the user to specify a cache mode, so that
they can get the block limits for the cache mode they intend to use with
their VM.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20251024123041.51254-5-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>