[FIX] mrp: check SN uniqueness on WO

When marking a WO as done, if the serial number defined is related to an
unbuilt product, an error will be raised and the user will not be able
to mark the WO as done

To reproduce the issue:
1. Create a BoM for product P with one operation
    - P is tracked by SN
2. Produce one P with serial S
3. Unbuild it
4. Create and confirm a second MO with 1 x P
5. Start the WO
6. On tablet view, set the finished lot to S
7. Mark the WO as done

Error: a UserError is raised because "This serial number [...] has
already been produced". However, this serial number has been unbuilt so
the worker should be able to use it again

When marking the WO as done, we check the uniqueness of the defined
serial number. But:
- The check is not accurate enough, hence the above error
- The lot of the WO is a computed/inverse field based on lot of the MO
- Once the WO closed, we can still change the lot of the MO
- When marking the MO as done, a better method checks the SN uniqueness
(does not fail in the above case)

Therefore, the checking on WO side is useless. We should let the MO side
handle this.

Moreover, let's say that there is already one P in stock with serial S2.
On tablet view, if the worker set the lot to S2, there should be a
warning so he can be aware of the situation. This is already the case on
MO side:
https://github.com/odoo/odoo/blob/45e37b2ad7bdcfd9f9f7e1dabbd0a99c9a0b5cdc/addons/mrp/models/mrp_production.py#L694-L705



(This commit is linked to a similar commit OE side, same opw)

OPW-3002424

closes odoo/odoo#104456

Related: odoo/enterprise#33377
Signed-off-by: Tiffany Chang <tic@odoo.com>