[BUGFIX] Filter undefined values from request payload

To keep compatibility with existing code, the AJAX API now removes
undefined values from any payload (either JSON, FormData or
SearchParams).

Resolves: #90310
Related: #89740
Releases: master
Change-Id: I5f36c566036739b62631e3838e8cbdecb46084fc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63167


Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>