[ADD]stock: add new fields for default unit of measure of product in sto...

...ck quants

Task: https://www.odoo.com/web#id=10993&view_type=form&model=project.task&menu_id=3942&action=327
PAD: https://pad.odoo.com/p/r.FYTSi7DmgYcnzHRy
Not stored ? For searches for example ?