[IMP] stock: allow changing operation type in draft

Rationale: if our users want to do a pick-pack-ship manually, they were
unable to duplicate pickings by just changing the operation type.

Task: 3290154
Related task: 3010731

Part-of: odoo/odoo#122511

addons/stock/models/stock_picking.py

@@ -506,8 +506,9 @@ class Picking(models.Model):
         for picking in self:
             picking.has_deadline_issue = picking.date_deadline and picking.date_deadline < picking.scheduled_date or False
 
+    @api.depends('state')
     def _compute_hide_picking_type(self):
-        self.hide_picking_type = self.env.context.get('default_picking_type_id', False)
+        self.hide_picking_type = self.state != "draft" and self.ids and 'default_picking_type_id' in self.env.context
 
     @api.depends('move_ids.delay_alert_date')
     def _compute_delay_alert_date(self):

addons/stock/views/stock_picking_views.xml

@@ -208,7 +208,7 @@
                             <field name="partner_id" nolabel="1" readonly="state in ['cancel', 'done']"/>
                             <field name="picking_type_id" options="{'no_open': True}"
                                    invisible="hide_picking_type"
-                                   readonly="id"
+                                   readonly="state != 'draft' and id"
                                    domain="context.get('restricted_picking_type_code') and [('code', '=', context.get('restricted_picking_type_code'))] or [(1,'=',1)]"/>
                             <field name="location_id" groups="!stock.group_stock_multi_locations" invisible="1" readonly="state == 'done'"/>
                             <field name="location_dest_id" groups="!stock.group_stock_multi_locations" invisible="1" readonly="state == 'done'"/>