[FIX] crm: don't bypass access right to find partner:

Problem
-------

Sales people can have restriction on partner they can see
Private addresses, multi company, ....

When they convert a lead to opportunity, it's currently possible
that the wizard will find and link a partner that the current user
cannot see.

Solution
--------
Field that are now computed store field, that were previously
normal field with onchange, should not be computed as sudo
to respect the record rule

closes odoo/odoo#59517

X-original-commit: af9db1d2aa605d46b5b5dae3d63533367c431f33
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>