[FIX] mrp: configure in and out moves of draft MO

In multi steps configurations, the additional products of a MO could be
missing in the associated picking

To reproduce the issue:
(Use demo data)
1. In Settings, enable "Multi-Step Routes"
2. Update the current warehouse:
    - Manufacture: 2 steps
3. Create a MO for product "Table Top"
4. Edit the MO:
    - Add 1 x Screw in the components
5. Confirm the MO
6. Open the generated Picking

Error: The operations only contains one line for "Wood Panel". There
should be a second line for the "Screw"

When adding the new component, a new stock move is created but the
latter does not have any `group_id` defined. This is the reason why the
generated picking does not include this stock move.

OPW-2671995

closes odoo/odoo#79759

Signed-off-by: William Henrotin (whe) <whe@odoo.com>