Migrate the existing checker / suggester code to instead use the new validator framework. We need to add,

• Printf validator (insertable but not enforced)
• Brace balance validator (insertable but not enforced)
• HTML insertables suggester

We'll need to update the YAML configuration file located here - https://phabricator.wikimedia.org/diffusion/GTWN/browse/master/groups/

Documentation: https://www.mediawiki.org/wiki/Help:Extension:Translate/Validators

Example patch: https://gerrit.wikimedia.org/r/c/translatewiki/+/549930