- Fix tends to prevent precision overflow in forecasted report

Current behavior before PR:
- If there are 2 units in stock and product_uom_qty is set to 0.66 the free_stock will be equal to 1.3399999999999999

Desired behavior after PR is merged:
- If there are 2 units in stock and product_uom_qty is set to 0.66 the free_stock should be equal to 1.34

opw-2425473
opw-2459650
opw-2448443
opw-2446985
opw-2440853
opw-2464507

closes odoo/odoo#70287

Signed-off-by: Rémy Voet <ryv-odoo@users.noreply.github.com>