[IMP] mrp: add indexes in mrp.workcenter.productivity model

We add a index on the workcenter_id and workorder_id, both
have a One2many related to  (`time_ids` of workcenter and workorder)
and both is in the some search domain in python (also in search view).
(Also change the `readonly='True'` into correct form `readonly=True`
of `production_id`, and remove duplicate fields `workcenter_id` in view)

task-2389380

closes odoo/odoo#63500

Related: odoo/upgrade#2042
Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>

addons/mrp/models/mrp_workcenter.py

@@ -308,12 +308,12 @@ class MrpWorkcenterProductivity(models.Model):
             company_id = self.env.company
         return company_id
 
-    production_id = fields.Many2one('mrp.production', string='Manufacturing Order', related='workorder_id.production_id', readonly='True')
-    workcenter_id = fields.Many2one('mrp.workcenter', "Work Center", required=True, check_company=True)
+    production_id = fields.Many2one('mrp.production', string='Manufacturing Order', related='workorder_id.production_id', readonly=True)
+    workcenter_id = fields.Many2one('mrp.workcenter', "Work Center", required=True, check_company=True, index=True)
     company_id = fields.Many2one(
         'res.company', required=True, index=True,
         default=lambda self: self._get_default_company_id())
-    workorder_id = fields.Many2one('mrp.workorder', 'Work Order', check_company=True)
+    workorder_id = fields.Many2one('mrp.workorder', 'Work Order', check_company=True, index=True)
     user_id = fields.Many2one(
         'res.users', "User",
         default=lambda self: self.env.uid)

addons/mrp/views/mrp_workcenter_views.xml

@@ -499,7 +499,6 @@
         <field name="model">mrp.workcenter.productivity</field>
         <field name="arch" type="xml">
             <search string="Operations">
-                <field name="workcenter_id"/>
                 <field name="workcenter_id"/>
                 <field name="loss_id"/>
                 <separator/>