[FIX] stock: clean quants after moving package

When moving a package, the quant at source location is not
automatically removed

To reproduce the issue:
1. In Settings, enable
   - Packages
   - Storage Locations
2. Create a storable product P
3. Update the on hand quantity
   - 1 x P at WH/Stock in package PK
4. Create a planned delivery D with 1 x P
5. Confirm and reserve D
   - PK should be reserved
6. Validate
7. Open the package
   - Its location is "Partner Locations/Customers", which make sense
8. Inventory > Configuration > ... > Locations, open WH/Stock
9. Current Stock

Error: There is a line with PK. The quantity is 0 but still, it
create some confusion for the user who could believe that the package
is still in WH/Stock

This issue does not occur if the user goes through the product form
and click on the on hand quantity. The "incorrect" quant will not be
there. This is because, when loading the action, we call
`_quant_tasks`:
https://github.com/odoo/odoo/blob/05a7f5c04804423cfc3a833a1b3f0b5eec3fc147/addons/stock/models/stock_quant.py#L296-L300
This method will clean the quants (merge & unlink)

However, in the above case (step 9), the action is defined on XML side:
https://github.com/odoo/odoo/blob/7d4dfeb0e26b387dee312897264a68963f90267f/addons/stock/views/stock_location_views.xml#L24-L26
https://github.com/odoo/odoo/blob/d956e719d43c68abe6210e3136db576aaa6f60b8/addons/stock/views/stock_quant_views.xml#L190-L196


So, we can't make it behave as it does from the product form,
unfortunatly.

As alternative, we can try to call `_unlink_zero_quants` when we are
moving a package (and not `_quant_tasks` for perf matters as, so far,
we will not have any quant to merge)

OPW-3292238

closes odoo/odoo#122768

X-original-commit: 5fb84ba5
Signed-off-by: William Henrotin (whe) <whe@odoo.com>