[FIX] point_of_sale: invoicing error at first invoiced order

To reproduce, open a pos session. Finalize an order with invoicing.
Error message is shown.

Invoicing in pos calls doAction of the action manager. The first time
doAction is called, it triggers a chain of events and a side effect
of that chain is to instantiate two mail owl components which isn't
possible because not all mail assets are loaded. A very quick fix is
to bypass that mentioned chain of events by setting isStarted flag to be
true. Aside from bypassing the instantiation of mail components, there
are procedures that were skipped as well which includes:

1. setting the bus to listen to scroll events
2. setting odoo.isReady to true
3. adding a class to the action manager element

All of the above is not important in pos and can be skipped so this
quick fix is valid. However, this fix doesn't actually solve the real
problem which is the fact the pos is loading unnecessary assets.

This commit implements the quick fix. Cleaning up pos assets will be
done in the future.

closes odoo/odoo#54478

Signed-off-by: pimodoo <pimodoo@users.noreply.github.com>