[REF] mass_mailing: prepare mass_sms

PURPOSE

SMS are a powerful marketing tool. For instance it is perfect to announce a
sale or to communicate a coupon code, to welcome a new customer in a fidelity
program, ...

Purpose of this task is to integrate SMS sending in batch in mass mailing. It
will use same mailing objects but sending SMS instead of emails. Some metrics
and flows will have to be slightly updated at the same time.

SPECIFICATIONS

Prepare mass mailing module to addition of mass_mailing_sms.

Mailing model: mailing type
  * add a mailing_type selection field;
  * mass mailing contains only 'mail';
  * synchronize medium accordingly;
  * update actions of mass mailing application to add a domain on mailing
    type being 'mail';

Mailing contact
  * remove is_email_valid field as its purpose is achieved by email_normalized
    field coming from address mixin (added by blacklist management);

Mailing contact subscription
  * clean a bit fields and views as this should stay a technical model;

Trace model and report: trace type
  * add a trace_type selection field;
  * mass mailing contains only 'mail';

Various
  * clean some bits of code in views, remove old code bits;
  * add anchors to ease view inheritance to be able to customize views for
    SMS mailings;
  * ensure all views in mass mailing filter content on mail type (mailing
    and traces being type mail only);
  * rename some methods to be more updated with current guidelines, notably
    main action methods;

LINKS

Task 1997464
PR #34424
Original SMS addition: Task 1922163 (4287481b)