[BUGFIX] EXT:form - wrong attribute handling

* centralize the attribute rendering method
* fix the attribute overlay methods
** fix: "select" labels remains empty
** fix: "textblock" remains empty

Resolves: #69957
Releases: master
Change-Id: I60554dbdf1eb8a25b9dfad820a2bc7bd20704199
Reviewed-on: http://review.typo3.org/43471


Reviewed-by: Frans Saris <franssaris@gmail.com>
Tested-by: Frans Saris <franssaris@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>