[BUGFIX] Manipulation of file field migration config

This patch introduces new methods to the FrontendContentAdapterServer
that allow the manipulation of the file field migration configuration.
It is now possible to add additional (content) types for which the
migration should be active and to add custom migration configurations.

Releases: 6.2
Resolves: #46067
Documentation: #56365
Change-Id: Ibc23be8a414192c8795d9bb4f09316cf608e240b
Reviewed-on: https://review.typo3.org/23360
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Tested-by: Tom Peters
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind