[BUGFIX] IRRE children's children are not moved with parent

Having a parent-child structure spanning three levels, only the
first and second level elements are moved to a different page.
All child elements below the second level are not changed.

The reason is, that the move-placeholder is only created for
the first level of children.

Resolves: #59111
Releases: 6.2
Change-Id: Ia044a1241b8b1e4885cabbbc44b777f847b4c9e5
Reviewed-on: https://review.typo3.org/30463
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader