When computing `qty_to_order` 1-3 extra queries are made by `get_lead_days()`, which can cause performance issues when computing `qty_to_order` for a large number of orderpoints.

This commit aims to prevent these extra queries by returning early if the current product is not associated with a bom. The amount this commit speeds up the compute depends on how many of products passed into `_get_lead_days()` are associated with a bom.

`qty_to_order` is no longer a stored field after this commit: https://github.com/odoo/odoo/pull/159432
This benchmark was done in 18.0 on /stock.warehouse.orderpoint/search_panel_select_range. This call does not trigger the compute on all orderpoints in 17.0 as the field is stored but calling the compute directly on all orderpoints results in the same speed up as seen in 18.0.

| Orderpoints | % of products linked to a bom | Time before | Queries before | Time after | Queries After |
|-------------|-------------------------------|-------------|----------------|------------|---------------|
|         800 | 50%                           | 2.8s        |           1570 | 2.3s       |           818 |
|       8,000 | 0%                            | 28.2s       |         16,698 | 15.3s      |           242 |
|       8,000 | 25%                           | 29.6s       |         16,833 | 19.2s      |          4497 |
|       8,000 | 50%                           | 29.8s       |         16,925 | 23.2s      |          8693 |
|       8,000 | 75%                           | 31.6s       |         16,949 | 27.6s      |         12827 |

Forward-Port-Of: odoo/odoo#262321