qemu-img: create: refresh options/--help (short option change)

Create helper function cmd_help() to display command-specific
help text, and use it to print --help for 'create' subcommand.

Add missing long options (eg --format) in img_create().

Recognize -B option for --backing-format, keep -F for
backward compatibility,

Reorder options for consistency.

Remove usage of missing_argument()/unrecognized_option() in
img_create().

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Message-ID: <20250531171609.197078-6-mjt@tls.msk.ru>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2 files changed