[FIX] mrp: reordering rules for BoM product

When running the scheduler, if one of the concerned product  is a
kit, it will always generate a RfQ for the components, even if there
are already enough of them.

To reproduce the error:
(Need purchase)
1. Create 2 products P and P_compo
	- Both must be storable products
	- P_compo must have at least one vendor
2. Go on P-product page
3. Add a reordering rule (e.g., min: 5 and max: 10)
4. Add a BoM
	- Must be a Kit
	- Add P_compo to components
5. Inventory > Operations > Run Scheduler
6. Go to Purchase, find the generated RfQ
7. Confirm the order, Receive Products, Validate
8. Go on P-product's page
	- As you can see, you have enough P-products on hand
9. Repeat steps 5-6

=> You should not find any RfQ since you already have enough P-products.

When checking the P-product's page, you can see the correct quantity on
hand because it uses the `_compute_quantities` method and this one has been
overridden in the mrp-module so a kit will be correctly computed.

However, when running the scheduler, it uses another method to get the
current quantities: `_compute_quantities_dict`. Since this method has
not been overridden in mrp-module, it will use the basic implementation
and this one does not consider the possibility for a product to be a
kit.

This fix creates an override of `_compute_quantities_dict` so it can
compute the correct quantities of products with 'phantom' as BoM type.
Moreover, for the code to be simpler and clearer, thix fix also merges
`_compute_quantities` and the new `_compute_quantities_dict`.

OPW-2421841

closes odoo/odoo#63891

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>