[ADD] product_main_seller: Restore OCA addon from original version

- Restored product_main_seller addon to fix dependency chain
- Addon required by product_origin_char and website_sale_aplicoop

[IMP] website_sale_aplicoop: Add demo data configuration to manifest

- Updated __manifest__.py to include demo data files
- Demo data includes partners, suppliers, products, group orders, and sale orders
- Demo data successfully loads during module installation

product_main_seller/views/view_product_template.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!--
+Copyright (C) 2022 - Today: GRAP (http://www.grap.coop)
+@author: Quentin DUPONT (quentin.dupont@grap.coop)
+License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
+-->
+<odoo>
+    <record id="view_product_template_search" model="ir.ui.view">
+        <field name="model">product.template</field>
+        <field name="inherit_id" ref="product.product_template_search_view" />
+        <field name="arch" type="xml">
+            <field name="categ_id" position="after">
+                <field name="main_seller_id" />
+            </field>
+            <filter name="categ_id" position="after">
+                <filter
+          string="Main Vendor"
+          name="main_seller_id"
+          context="{'group_by':'main_seller_id'}"
+        />
+            </filter>
+        </field>
+    </record>
+
+    <record id="view_product_template_tree" model="ir.ui.view">
+        <field name="model">product.template</field>
+        <field name="inherit_id" ref="product.product_template_tree_view" />
+        <field name="arch" type="xml">
+            <field name="list_price" position="before">
+                <field name="main_seller_id" optional="show" />
+            </field>
+        </field>
+    </record>
+</odoo>