[IMP] base_import: Defer parent computation after record creation/update

Currently when importing files, the parent left and right are recomputed on each record creation/update, which could lead to a lot a request.

This commit will defer the parent field recomputation to the end on the `load` function by recomputing the values from the MPTT and inserting directly the new values on the records.

Tested on a customer instance, this will reduce the execution time when importing a thousand stock.location from 15 minutes to several seconds.

addons/base_import/models/base_import.py

@@ -664,7 +664,13 @@ class Import(models.TransientModel):
             }]
 
         _logger.info('importing %d rows...', len(data))
-        import_result = self.env[self.res_model].with_context(import_file=True).load(import_fields, data)
+
+        model = self.env[self.res_model].with_context(import_file=True)
+        defer_parent_store = self.env.context.get('defer_parent_store_computation', True)
+        if defer_parent_store and model._parent_store:
+            model = model.with_context(defer_parent_store_computation=True)
+        
+        import_result = model.load(import_fields, data)
         _logger.info('done')
 
         # If transaction aborted, RELEASE SAVEPOINT is going to raise