MDL-83509 adds new launch builders, replacing some of the \core_ltix\helper:: methods dealing with launch. Firstly, if not already done in 83509, these methods should be removed from core_ltix where possible (assuming they're not still used for any part of the launch, e.g. a legacy launch flow).

Secondly, mod_lti still may have deprecated methods calling these now-defunct core_ltix helper methods. In this case, deprecation makes no sense, since the replacement will be deleted. So, instead of deprecation inside mod_lti, we'll need to delete the method entirely.