The `fetchmail` module is build on top of the `mail` module and enables the incoming email capabilities. However, using the `mail` without incoming email server is not a good use case. This commit merges the `fetchmail` moudule into `mail` and lessens the module complexity, along with adapting the xml/external ids in the dependent modules. task-2797458 closes odoo/odoo#94143 Related: odoo/upgrade#3615 Related: odoo/enterprise#28659 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>