[REF] stock: make picking button_validate multi

So we have to adapt
- the sanity checks
- the immediate/backorder wizards
- split the call to _action_done with and without backorder

This is a preliminary work to remove all the override in
stock_picking_batch and to allow choosing the pickings to immediate or
backorder directly in the wizards.

Before this commit, both wizards were calling _action_done and one
another. We make them go back through `button_validate` so that it is
more sane to handle and allow future extensions to add pre-action done
wizards.

Also the first part of button_validate is some sanity check. We adapt
them to be multi (inside of a loop over self) without any other
changes.

Now the wizard can work on the records (immediate: write the done
quantities) or work with the context (backorder: picking ids to not
backorder in the context).

Also we adapt the stock sms weird wizard (a confirmation wizard but the
feature is auto installed? wth). Now there it isn't manually called in
the middle of button_validate but it uses the pre_action_done_hook.

task-2069646