Remove classes from system templates r*.html.twig

Problem/Motivation

Remove non essential classes from core - the classes are in classy, cores templates should be as clean as possible.
js required classes should be prefixed to js- according to code standards
simpletest should be done with classy theme, not stark

See parent issue(s) and related issue(s) for details,

Proposed resolution

Twig Templates to modify

• core/modules/system/templates/radios.html.twig
• core/modules/system/templates/region.html.twig

Remaining tasks

User interface changes

API changes