Before this commit, the A/B testing cron was active by default.
It doesn't matter if A/B testing is true or false in settings.
So, with this commit, we set active equals to false by default
in the A/B testing cron. It will be active when the user sets
`group_mass_mailing_campaign` to True.
TaskId-2713198
X-original-commit: b348f8658f87c15d0fe4ee72888e99da2a529700
Part-of: odoo/odoo#107488
PURPOSE
Reorganize addon according to guidelines, helping finding and updating code.
SPECIFICATIONS
Correctly split data into separate files. A lot of content was put a bit
randomly in data files, leading to a hard discovery of code and features.
We also fix duplicated attachments definition, both in mass_mailing_data and
ir_attachment files. It has been merged into the attachment data file.
Task-2864264 (Mass Mailing Module Reorganization)
Part-of: odoo/odoo#92509
dht-odoo