[FIX] sale: Add indexes on some fields

Once sale_project is installed, when trying to add/remove an employee on
the "Invoicing" tab on the project form view for a big internal project,
this decreases the execution time from 20 minutes / timeout to 12 seconds,
by decreasing drastically the execution time of _get_last_sol_of_customer
on sale_line_id recomputation (_compute_sale_line).

closes odoo/odoo#90263

Taskid: 2836314
X-original-commit: 757358449b7514f371415c528b818020f6147335
Signed-off-by: Laurent Stukkens (ltu) <ltu@odoo.com>

addons/sale/models/sale_order_line.py

@@ -47,7 +47,7 @@ class SaleOrderLine(models.Model):
     order_partner_id = fields.Many2one(
         related='order_id.partner_id',
         string="Customer",
-        store=True, precompute=True)
+        store=True, index=True, precompute=True)
     salesman_id = fields.Many2one(
         related='order_id.user_id',
         string="Salesperson",