Following on from T257265, Minerva loads mediawiki.page.ready and as a result the library for checkboxHack

https://github.com/wikimedia/mediawiki/blob/master/resources/src/mediawiki.page.ready/checkboxHack.js

Despite this it seems to duplicates some of the code in https://github.com/wikimedia/mediawiki-skins-MinervaNeue/blob/master/components/ToggleList/ToggleList.js

1. Acceptance criteria
2. A new default off feature is added to ResourceLoaderSkinModule called "checkbox-hacks" which provides helper CSS for the checkbox hack CSS that's common to Vector and Minerva.
3. Minerva has opted into the feature and removed its now redundant CSS
4. Vector has opted into the feature and removed its now redundant CSS