Currently on stock moves, product_uom_qty indicates the demand qty
before the move is done and it indicates the acutual done qty when
the move is done.
As a result, when validate a stock move with qty_done !=
product_uom_qty, a new move is always created for the difference.
And the product_uom_qty of the original move will be changed to match
qty_done.
In this commit, we change to that product_uom_qty will always indicate
the demand qty, and qty_done will always indicate actually done
quantity.
To do that, when underconsumption, we won't split the move when no
backorder. and when overconsumption, we will always merge the extra move
back to the original move.
Task-2695732
Part-of: odoo/odoo#130342
yhu-odoo
f9867a5fa5