[FIX] product: delete Package when associated product is deleted

Steps to reproduce:
- Enable product packaging
- Create a Package for product P and set the barcode
- Delete product P
- Create a new Package with the same barcode

Bug:
barcode already exists

Fix:
delete Package when associated product is deleted

opw-3507931

closes odoo/odoo#136305

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