The main classes of partners and users support batch creation, but
the majority of their overrides doesn't support creation in batch.
Adapting those overrides to support records creation in batch shows
great performance gains:
* On `res_partner` : 2 to 3 times faster
* On `res_users`, with the inherited `res_partner` created in batch:
up to 10 times faster.
Tests done with 500 to 4k records:
* `res_partner` with only a name provided
* `res_users` with a name and login
X-original-commit: 9c3c5f161580039c1fe50f68acac808c18817997
Victor Feyens
e3c329b9bc