Function build_encoded_bundle 

pub fn build_encoded_bundle(
    package: &WorkPackage,
    extrinsics: &[Vec<Vec<u8>>],
    imports: &[Vec<ImportData>],
) -> (WorkPackageHash, Vec<u8>)

Construct an encoded Work Package Bundle from its parts

This function assumes the number of extrinsics and imports matches the Work Package and does not explicitly check that fact. package - Work Package, extrinsics - One element for each Work Package item. Each element contains a vector of extrinsic data for that item. imports - One element for each Work Package item. Each element contains a vector of import data for that item. Returns encoded package hash and the econded bundle.