[TASK] Cleanup sysext "tstemplate" and module functions

Change-Id: Icd9ad7fadbd6910eba87a77908e15568be800dc2
Resolves: #46144
Releases: 6.1
Reviewed-on: https://review.typo3.org/18821
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn