[IMP] sale_stock,sale_mrp: available quantities on sales order

Selling a product you don't have in stock anymore triggers a message
without pertinent information about available quantity.

This commit adds a little widget on sale order line to inform the salesman
there are not enough quantity available. Clicking on it will reveal:
* The estimated delivery date
* The actual quantity on hand
* The quantity forcasted at the estimated delivery date

For kit product, the quantities are the maximum occurence of kit available
regarding components quantities.

Task 2003485

closes odoo/odoo#34336

Signed-off-by: Simon Lejeune (sle) <sle@openerp.com>