[!!!][TASK] Remove internal_type=file/file_reference

This drops TCA type=group with internal_type=file and
internal_type=file_reference handling.
This patch is rather huge since detail handling of this
stuff is spread throughout the core. Additionally, some
further methods become unused and oboselete along the way.
Most of them - except DataHandler->process_uploads() - have
been used internally only and can be safetly dropped,
while process_uploads() which has always been part of the
externally called API is substituted with a no-op method.

Resolves: #87428
Releases: master
Change-Id: Ia60b5d0e021b34adf4b4187a5f1fe4475b0070b4
Reviewed-on: https://review.typo3.org/59361
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <noreply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>

Classes/DataHandling/FrontendEditDataHandler.php

@@ -300,7 +300,6 @@ class FrontendEditDataHandler
         if (!empty($data)) {
             $dataHandler = GeneralUtility::makeInstance(DataHandler::class);
             $dataHandler->start($data, []);
-            $dataHandler->process_uploads($_FILES);
             $dataHandler->process_datamap();
             // Save the new UID back into configuration
             $newUID = $dataHandler->substNEWwithIDs['NEW'];