[FEATURE] Allow stdWrap on form-element-defaultvalues

Allow "value"-parameter (initial value) for a form-element
to be modified using stdWrap (fetch data from somewhere,
modify, ...).

Change-Id: Id1a4f25758bf7aa1632bdd3bd9b37761252b463a
Resolves: #38163
Releases: 6.1
Reviewed-on: https://review.typo3.org/12190
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn