[TASK] SelectSingleElement merge methods

This patch removes the private property resultArray and merges
the function getSingleField_typeSelect_single into the render()
method.

Releases: master
Resolves: #69726
Change-Id: I3a8a230d3a61046652684f7ae68568e72d892e8f
Reviewed-on: http://review.typo3.org/43255


Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>