This commits adds the sanitization right before the data is added to the
database (\MailPoet\Segments\SegmentsRepository::createOrUpdate()) and
removes the sanitization from
\MailPoet\Segments\DynamicSegments\SegmentSaveController::save() to
avoid sanitizing twice. save() calls createOrUpdate().
Before this commit, we were sanitizing the name and description of
dynamic segments but not regular segments.
[MAILPOET-5232]
