[TASK] Add basic unit test for IRRE form rendering

The basic information in IRRE are the repeatable triples of
table-uid-field. This test ensures to have a working separation
of stable and unstable segments available.

Change-Id: Ie0a0e87faf4c4e7a41fb6aed01af6610f12b1c7f
Resolves: #42702
Releases: 6.0
Reviewed-on: http://review.typo3.org/16209
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader