Add new MutableCompositeModification version

MutableCompositeModification requires use of NormalizedNodeDataInput.newDataInputWithoutValidation() due to how it handles multiplexing of the data stream – modification type is written into the normal data stream and the modification itself is written into the NormalizedNodeDataOutput overlay. This has a weird effect that the first modification type is before the NNDO header.

Introduce a new version, which will get rid of this abomination by using NNDO directly, without interspersing. This will result in the NNDO header being written just after the number of modifications and before any type – thus forming a proper embedded block.