[FW][FIX] crm: fix team_count computation at create

When stage is being created, `team_count` was not computed, because it
has not dependencies. This means the "sales team" field is not displayed
which is annoying in multi team environment.

To workaround it a fake trigger is added.

Task-2917174
Closes odoo/odoo#87905

Part-of: odoo/odoo#95962