[IMP] mrp: use prefetch for recursive quantities computation

This commit achieves two things:

1) Avoid calling super() on an empty recordset, in case all products
   are kits. Even on an empty recordset, some queries would be fired.
   This commit avoids them.

2) Use prefetch to read kit components quantity fields, to make use
   of the recorset optimizations that ends up saving sql queries.
   Otherwise, component quantities were computed on-demand one by one.

closes odoo/odoo#93529

Signed-off-by: William Henrotin (whe) <whe@odoo.com>

addons/mrp/models/product.py

@@ -136,18 +136,33 @@ class ProductProduct(models.Model):
         """
         bom_kits = self.env['mrp.bom']._get_product2bom(self, bom_type='phantom')
         kits = self.filtered(lambda p: bom_kits.get(p))
-        res = super(ProductProduct, self - kits)._compute_quantities_dict(lot_id, owner_id, package_id, from_date=from_date, to_date=to_date)
+        regular_products = self - kits
+        res = (
+            super(ProductProduct, regular_products)._compute_quantities_dict(lot_id, owner_id, package_id, from_date=from_date, to_date=to_date)
+            if regular_products
+            else {}
+        )
         qties = self.env.context.get("mrp_compute_quantities", {})
         qties.update(res)
+        # pre-compute bom lines and identify missing kit components to prefetch
+        bom_sub_lines_per_kit = {}
+        prefetch_component_ids = set()
         for product in bom_kits:
-            boms, bom_sub_lines = bom_kits[product].explode(product, 1)
+            __, bom_sub_lines = bom_kits[product].explode(product, 1)
+            bom_sub_lines_per_kit[product] = bom_sub_lines
+            for bom_line, __ in bom_sub_lines:
+                if bom_line.product_id.id not in qties:
+                    prefetch_component_ids.add(bom_line.product_id.id)
+        # compute kit quantities
+        for product in bom_kits:
+            bom_sub_lines = bom_sub_lines_per_kit[product]
             ratios_virtual_available = []
             ratios_qty_available = []
             ratios_incoming_qty = []
             ratios_outgoing_qty = []
             ratios_free_qty = []
             for bom_line, bom_line_data in bom_sub_lines:
-                component = bom_line.product_id.with_context(mrp_compute_quantities=qties)
+                component = bom_line.product_id.with_context(mrp_compute_quantities=qties).with_prefetch(prefetch_component_ids)
                 if component.type != 'product' or float_is_zero(bom_line_data['qty'], precision_rounding=bom_line.product_uom_id.rounding):
                     # As BoMs allow components with 0 qty, a.k.a. optionnal components, we simply skip those
                     # to avoid a division by zero. The same logic is applied to non-storable products as those