[FW][FIX] mass_mailing: check fields for seen list are stored before going into SQL

Seen list (aka already mailed records) computation is done in SQL to speedup
computation. It is based on an heuristic to find fields to check (either
a partner, either an email). However it checks fields are present in model
but does not check they are stored. This leads to traceback if fields
are not stored.

Task-2852943

X-original-commit: odoo/odoo@0a2420f08bc18c5b93a54f387b062b405d3c2453
Part-of: odoo/odoo#91533