[FIX] point_of_sale: make sure cash moves are not duplicated

Current behavior:
When your connection is slow and you try to create a cash move, and you
click multiple times on the confirm button. The cash move is created
multiple times.
This happens because the function is not locked while the asynchronous
call is not finished. To fix this we added a custom hook to lock the
function while the asynchronous call is not finished.

Steps to reproduce:
-Open the POS
-Press F12 and in the network tab of the developper tools, set the
 connection to slow 3G
-Open the cash move popup, enter an amount and click on confirm multiple
 times.
-Close the session, and check the cash moves created.

opw-3431775

closes odoo/odoo#130735

Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>