Style guide: checkboxes and radio buttons

The code in the user.permissions.js file has been changed, and it now removes the form-checkbox CSS class.

// Create fake checkboxes. We use fake checkboxes instead of reusing
// the existing checkboxes here because new checkboxes don't alter the
// submitted form. If we'd automatically check existing checkboxes, the
// permission table would be polluted with redundant entries. This is
// deliberate, but desirable when we automatically check them.
const $fakeCheckbox = $(Drupal.theme('checkbox'))
  .removeClass('form-checkbox')
  .addClass('fake-checkbox js-fake-checkbox')
  .attr({
    disabled: 'disabled',
    checked: 'checked',
    title: Drupal.t(
      'This permission is inherited from the authenticated user role.',
    ),
  });
const $wrapper = $('<div></div>').append($fakeCheckbox);
const fakeCheckboxHtml = $wrapper.html();

We should implement code similar to the one used by the Claro theme.