This commit adds a new group `ab_test_group` after notebook of campaign form
view, which displays A/B test related information. Below are the fields
displayed within the group:
- ab_testing_winner_selection
- ab_testing_schedule_datetime
They will become readonly as soon as the the A/B testing is completed.
Apart from that, this commit makes the mailing/sms mailing lines editable.
TaskID-2653806
Part-of: odoo/odoo#77768