[IMP] crm : align partner action in lead to opportunity modal on New quotation modal

For consistency, in the 'convert to opportunity' modal,
move the 'create a new customer' at the top of the selection values
to be align with the New quotation - set partner modal
(crm.quotation.partner)
+ change the group title to 'Customer' instead of 'Customers'

Task ID : 1917332
Closes PR #30475

addons/crm/wizard/crm_lead_to_opportunity_views.xml

@@ -29,7 +29,7 @@
                             </tree>
                         </field>
                     </group>
-                    <group name="action" attrs="{'invisible': [('name', '!=', 'convert')]}" string="Customers" col="1">
+                    <group name="action" attrs="{'invisible': [('name', '!=', 'convert')]}" string="Customer" col="1">
                         <field name="action" nolabel="1" widget="radio"/>
                         <group col="2">
                             <field name="partner_id" widget="res_partner_many2one" domain="[('customer', '=', True)]" context="{'search_default_customer': 1, 'show_vat': True}" attrs="{'required': [('action', '=', 'exist')], 'invisible':[('action','!=','exist')]}"/>

addons/crm/wizard/crm_partner_binding.py

@@ -29,8 +29,8 @@ class PartnerBinding(models.TransientModel):
         return res
 
     action = fields.Selection([
-        ('exist', 'Link to an existing customer'),
         ('create', 'Create a new customer'),
+        ('exist', 'Link to an existing customer'),
         ('nothing', 'Do not link to a customer')
     ], 'Related Customer', required=True)
     partner_id = fields.Many2one('res.partner', 'Customer')