[IMP] partner_autocomplete: extract iap calls in a separate model and add a mock

In this commit we move iap functions onto a small tool model. It allows to
hide some details in a sub model. It also allows to define a mock that will
be used in tests afterwards.

LINKS

Task ID-2322455
PR #64600
PR odoo/upgrade#2086

Co-Authored-By: David Beguin <dbe@odoo.com>
Co-Authored-By: Thibault Delavallee <tde@odoo.com>