Part of task 1896658

Co-authored-by: Aaron Bohy <aab@odoo.com>
Co-authored-by: Christophe Matthieu <chm@odoo.com>
Co-authored-by: Mathieu Duckerts-Antoine <dam@odoo.com>
Co-authored-by: David Monjoie <dmo@odoo.com>
Co-authored-by: Martin Geubelle <mge@odoo.com>
Co-authored-by: svs-odoo <svs@odoo.com>
Co-authored-by: Vincent Schippefilt <vsc@odoo.com>

Loads the barcode nomenclature only if one has been is defined. Indeed,
from commit 80e89c7a11d16fa, the POS config unset the
`barcode_nomenclature_id` field if the barcode support is not activated.

opw-1859928

Before this commit, the JS parser would add 0 after the input, then add the ean key.
Whereas reportlab.graphics.barcode fills the input with 0's on the left, then add the key

http://pydoc.net/Python/reportlab/2.5/reportlab.graphics.barcode.eanbc/
At: Ean13BarcodeWidget.__init__()

This commit makes the ean parser coherent with the lib the python uses

The RPC system was not completely satisfactory, we decided to prepare
the future and do it properly.  This commit introduces the new rpc
system, which replace the previous new one.  We now simply have a
method, this._rpc, which takes a dictionary of parameters.  The idea is
that depending on the parameters, it is able to add correct default
value when necessary.

For situations where we don't have the this._rpc method, we can use the
rpc.query method, which takes the same arguments, but directly calls
ajax.rpc instead of triggering up some events.

The _rpc method is now the preferred method to do a rpc, so we need to
update all calls.

Use this.rpc instead of Model object, with web.ajax if necessary.

nb: EventDispatcherMixin include now the custom_events managment instead
of widget

Causes issues with the card reader device.