purchase_lot: Removing sale_order_lot_selection dependency

[Tisho99]

Is your feature request related to a problem? The purchase_lot module depends on sale_order_lot_selection for the lots being propagated from sales to purchases. This is a very strong dependency and the module could be more versatile without it (also mentioned in https://github.com/OCA/purchase-workflow/issues/1538).

Describe the solution you'd like I'd like to replace the sale_order_lot_selection dependence for purchase_stock and stock_restrict_lot. With this, we would have lots in purchase order lines with less module dependences.

I think removing the readonly of the lot_id field is also useful to let users filling and creating the lot from the purchase order, now the module only propagates the lots from sales to purchases

Describe alternatives you've considered I have considered creating another bridge module that depends sale_order_lot_selection and the refactored purchase_lot, but i think it would not be neccesary because all the functions the module inherits are created in the purchase_stock module.

[Tisho99]

Hello @florian-dacosta

As I saw in the issue https://github.com/OCA/purchase-workflow/issues/1538, you agreed to remove the sale_order_lot_selection dependency from the purchase_lot module.

Do you still agree? We can do the PR.

Would you also agree to make the lot field editable?

Thank you for your time.