[TASK] Re-add tests for renumberKeys

The test for renumberKeysToAvoidLeaps were accidentally
removed. Add them again.

Change-Id: Ib51cc8f96d7745ae199ecd2c1e77d728611fde78
Resolves: #63986
Releases: master
Reviewed-on: http://review.typo3.org/35582
Reviewed-by: Stephan Großberndt <stephan@grossberndt.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>