PURPOSE Improve performances of various Odoo code bits. SPECIFICATIONS Use a read_group to compute the opportunities_count & opportunities_amount, like the other compute methods for statistics fields. Do the same improvement in pos_sale when computing pos_order_amount_total. LINKS Task ID-2281297 PR odoo/odoo#53053 PR odoo/enterprise#11299 X-original-commit: 3e30b1e5c1aa25463848d82492f25002bcbf9154