We can use ._search() to make sure that permissions and ir.rules are applied. By making use of psql subqueries, we remove the need of costly python filtering afterwards, thus increasing performance.

Created test_meeting_count() to check that that the computing of meeting_count is done correctly.

closes odoo/odoo#88460

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