[IMP]sale_crm: Add new button (“Sales“) on Opportunity form view.

Add new button (“Sales“) on Opportunity form view and display total amount of related quotes/sales on that stat button.

Task: https://www.odoo.com/web?#id=9370&view_type=form&model=project.task&menu_id=3942&action=327

Pad: https://pad.odoo.com/p/r.fvkticI2jioPxHls
Rename to _get_sale_amount_total