validator_groups: RuntimeDescriptor<
    [],
    [
        number[][],
        {
            group_rotation_frequency: number;
            now: number;
            session_start_block: number;
        },
    ],
>

Returns the validator groups and rotation info localized based on the hypothetical child of a block whose state this is invoked on. Note that now in the GroupRotationInfo should be the successor of the number of the block.