[FIX] {purchase_}stock, product: base product name on supplier

Suppose a product with several suppliers, all with the same partner. On
the purchase order, the product description will always be based on the
last supplier

To reproduce the issue:
1. Create a vendor V
2. Create a product P:
    - Type: Storable
    - In Purchase, add a line L01:
        - Vendor: V
        - Vendor Product Name: Name01
        - Vendor Product Code: C01
        - Quantity: 1
        - Price: 10
    - In Purchase, add a second line L02:
        - Vendor: V
        - Vendor Product Name: Name02
        - Vendor Product Code: C02
        - Quantity: 20
        - Price: 2
    - Once P is saved, ensure the lines order in the purchase tab:
        - L01
        - L02
3. Add a reordering rule on P:
    - Min: 1
4. Run the scheduler
5. Open the generated PO

Error: The description is incorrect ("[C02] Name02" instead of "[C01]
Name01")

When computing the display name of the product,
https://github.com/odoo/odoo/blob/7691567286869ca65e63fc79c2cee11e1f415fcb/odoo/models.py#L1728-L1730


`name_get` returns a tuples list: `[(37, '[C01] Name01'), (37, '[C02]
Name02')]` where `37` is the product identifier. This list is then
converted into a dictionary and here is the issue: it will use the last
tuple to define the value for key `37`, i.e. "[C02] Name02". Therefore,
`name_get` should return the correct name, and only this one.

Another issue could be highlighted: when the user changes the quantity
of the purchase order line, if another supplier info is selected, the
description won't be updated (for the same reason as above)

OPW-2702616

closes odoo/odoo#82049

Signed-off-by: Tiffany Chang <tic@odoo.com>