[TASK] Add addTop/removeTop row in backend layout wizard

Improve the backend layout wizard by providing additional buttons to
add and remove rows at the top.

Resolves: #80009
Releases: master
Change-Id: I85b2361cc63431e59f64265091323b2c6f2cf2b9
Reviewed-on: https://review.typo3.org/51870


Reviewed-by: Josef Glatz <josef.glatz@typo3.org>
Tested-by: Josef Glatz <josef.glatz@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>