Purpose
=======
Since v15, the time to import records in Odoo is much slower than in
v14. With a profiling, we know that the cause is `fields_get`. Indeed,
this method is heavy and call many times (#rows * #columns * ~#batches).
So the import time (in seconds) for ~1000 leads in CRM is;
Batch size | v14 | v15 | v15 fix
--------------------------------
2000 | 7 | 20 | 14
200 | 11 | 48 | 15
20 | 17 | 423 | 23
We can see that just by calling `._fields.get` instead of `fields_get`
we gain a lot of time. The reason for that is `fields_get` just read in
a python dictionary (which is really really fast), while `fields_get`
checks the access right, get the description of each fields (which
might make SQL queries to retrieve translation, etc).
Task-2687407
X-original-commit: 96e72a8b1657df00d5ed7ca6db7bd99e352d7096
Part-of: odoo/odoo#79913
std-odoo
8125165b00