[IMP] Stock Production Lot dissociate last_delivery_partner_id computation

In stock_production_lot model, there is a field last_delivery_partner_id which is displayed in a Tree View. This fields require to compute ALL the delivery_ids of each LOT, only to display the last_delivery_partner.

This implies a big performance issue for big lots with huge tracability needs in it. The idea is simple, dissociate the computation for delivery_ids, which is only used in Form View and the last_delivery_partner_id which is only used in the Tree View.

I do agree that if both are used in the same view, it would double the computation time. But currently there is a lot of useless computation. Currently the only way to mitigate is by removing the field last_delivery_partner_id in the Tree View, but if client needs that field, it doesn't works.

Benchmark

|Lots/Serial |# Lots | # Delivery | Before PR | After PR |
|:------------:|:---------:|:--------:|
|Lots| 3 | 3  | 0.2723 s |0.0091 s |
|Lots| 4 | 6699 | 307.98 s | 0.0059 s |
|Lots | 13 | 9575 | 569.85 | 0.0036 s |
|Serial | 80  | 80  | 0.30 s | 0.42 s |
|Serial | 150 | 150 |0.39 s | 0.51 s |
|Serial | 7000 | 2000 | 0.50 s/Batch of 1000 | 0.60 s/Batch of 1000|

closes odoo/odoo#129363

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