[REF+IMP] account_payment_order: Use native payments

The previous approach creates manually the journal entries and does all
the hard work, plus not being 100% compatible with the bank statement
reconciliation widget (requiring a patch on OCB to see blue lines).

That decision made sense on the moment it was done (v9), where the
native payment model (account.payment) was very limited, and wasn't able
to store all the needed information for the bank transaction.

Now that the limitations are gone, we can get rid off this extra model,
and generate instead `account.payment` records, using both the native
model + methods to perform the same operations.

This serves also to workaround the problem found in #966.

All the code, views and tests of main module have been adapted to this
new approach in this commit. Later commits will adapt the rest of the
modules of the suite, and add migration scripts to transit from the
previous approach to this new one.

TT39832

account_payment_order/data/payment_seq.xml

@@ -1,18 +1,10 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <!--
-  © 2015-2016 Akretion (https://www.akretion.com/)
-  @author: Alexis de Lattre <alexis.delattre@akretion.com>
-  Copyright 2019 Tecnativa - Pedro M. Baeza
+  Copyright 2015-2016 Akretion - Alexis de Lattre
+  Copyright 2019-2022 Tecnativa - Pedro M. Baeza
   License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl).
 -->
 <odoo noupdate="1">
-    <record id="bank_payment_line_seq" model="ir.sequence">
-        <field name="name">Bank Payment Line</field>
-        <field name="code">bank.payment.line</field>
-        <field name="prefix">L</field>
-        <field name="padding">5</field>
-        <field name="company_id" eval="False" />
-    </record>
     <record id="account_payment_line_seq" model="ir.sequence">
         <field name="name">Payment Line</field>
         <field name="code">account.payment.line</field>