[TASK] Move flexform definitions

Move flexform definitions to folder Configuration/Flexforms.

Resolves: #57616
Releases: 0.6
Change-Id: Ic962f12fd6d172f0a38566a1ffbc7552cac576b0
Reviewed-on: https://review.typo3.org/29127
Reviewed-by: Francois Suter
Tested-by: Francois Suter