Checkboxradio: Correctly assemble radio group

Closes gh-6659
Closes gh-7082
Fixes gh-7088
Collapsible: fix the bug about collapsedIcon

Closes gh-6708
Fixes gh-7089
Collapsible: Handle icon-related option setting uniformly

This adds tests for fbbb29e465d221b61cecef9c41aa74ec3e37df02

Closes gh-7081