Each requires 9.3 or 10

Also adds a deprecation for NULL in Gateway plugins.
Tests now make use of typed properties, and are final'ed.
Events now extend the new Symfony event. Usages should already be typehinting the SMS Framework class.

Some constructors changed. Changes to constructors are not considered API changes.

Issue #2797121 by dpi, nyariv, almaudoh: Separate entity phone number from verification service for flexibility