Splits the given element at the given offset without validation.
Should not be used directly. The "unsafe" part in this function only refers to the fact that the function does not do any validation, in contrast to primitives that always guarantee a schema-valid result on an unmodified blueprint.
The position on which the split is started remains in the first half.
The node to split
The offset at which to split the node
The blueprint in which to perform the operation
Whether to move the position from which the split was started into the second half
The second half of the split node. The given node becomes the first half.