[BUGFIX] Fix custom FormEngineValidation registrations

With #96597 custom evaluations registered via
FormEngineValidation.registerCustomEvaluation()
have no longer been evaluated as a condition related
to the unrelated and no longer always defined object
TBE_EDITOR.customEvalFunctions shadowed the condition for
JavaScriptModuleInstruction-style customEvaluations.

Resolves: #96782
Related: #96597
Releases: main
Change-Id: Iff9816af73d1584b41d7163f804dce7a6b2547b4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73351


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>