[FIX] purchase: Add 'price_total' & 'price_tax' to the order lines tree

# Description
The absence of those fields can generate a log note spam & performance issue when updating an order line value.

# HOW TO REPRODUCE
- Create PO with 40+ order lines (50 recommend) (* SA to reproduce would be nice)
- Confirm PO (state needs to be "purchase")
- Update the Ordered Quantity of the first line.
- Save
=> PO Lines from page 2 and beyond have each created the following log message:
"The ordered quantity has been updated."

# Explanation
The purchase.order.line onchange will not save any update on 'price_total' because it is not on the onchangeSpec.
Then a purchase.order onchange is done, and this one does have 'order_line.price_total' on the onchangeSpec, forcing the onchange method to return the field 'order_line' (aka ALL the order lines) as updated.
When saving the changes, the JS framework, who does not have the data for the order_lines on the 2nd page, will not correctly filter the fields with real changes, and add the 'product_qty' field (and more) to the "write" call for every order_line not in the 1st page.
Then the write method, without checking if there is any real change on the product_qty, for each lines that has product_qty in the Write's values, will write in the log note and call a performance intensive method: _create_or_update_picking()

OPW-2982004

closes odoo/odoo#104490

X-original-commit: e99cdd64
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: David <dafr@odoo.com>

addons/purchase/views/purchase_views.xml

@@ -250,6 +250,8 @@
                                     <field name="price_unit" attrs="{'readonly': [('invoice_lines', '!=', [])]}"/>
                                     <field name="taxes_id" widget="many2many_tags" domain="[('type_tax_use','=','purchase'), ('company_id', '=', parent.company_id)]" context="{'default_type_tax_use': 'purchase', 'search_view_ref': 'account.account_tax_view_search'}" options="{'no_create': True}" optional="show"/>
                                     <field name="price_subtotal" widget="monetary"/>
+                                    <field name="price_total" invisible="1"/>
+                                    <field name="price_tax" invisible="1"/>
                                 </tree>
                                 <form string="Purchase Order Line">
                                         <field name="state" invisible="1"/>