We need to move all maintenance scripts to use PHP 7.2 instead of HHVM.
This can be done by simply prepending `PHP=php7.2` to all the invokations of mwscript etc in the maintenance scripts.
What needs to be done in detail:
* Pick a few scripts to migrate first, notify the owners, migrate[] Separate production maintenance scripts from wikitech ones*
[] Pick a few scripts to migrate first, notify the owners, *migrate
[] Migrate the wikidata dispatcher
*[] Migrate all other scripts by setting php7.2 as the preferred debian alternative
*[] Revert all the modifications to the scripts above as we don't need to force
* Some cronjobs are shared with wikitech, which has not been switched to PHP7. To avoid blocking this task we can keep production and wikitech maint jobs separate
Related to: T219135: