[TASK] Improve namings of RadioElement

Resolves: #62034
Releases: master
Change-Id: I894923e9b84109b3b3badff3e94662a41e84d6d0
Reviewed-on: http://review.typo3.org/33165
Reviewed-by: Stefan Froemken <froemken@gmail.com>
Tested-by: Stefan Froemken <froemken@gmail.com>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>