submodule--helper: teach update_data more options

submodule--helper: teach update_data more options

Refactor 'struct update_data' to hold the parsed args needed by "git
submodule--helper update" and refactor "update-clone" and
"run-update-procedure" (the functions that will be combined to form
"update") to use these options.

For "run-update-procedure", 'struct update_data' already holds its args,
so only arg parsing code needs to be updated.

For "update-clone", move its args from 'struct submodule_update_clone'
into 'struct update_data', and replace them with a pointer to 'struct
update_data'. Its other members hold the submodule iteration state of
"update-clone", so those are unchanged.

Incidentally, since we reformat the designated initializers of the
affected structs, also reformat MODULE_CLONE_DATA_INIT for consistency.

Signed-off-by: Glen Choo <chooglen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>