debian: Add missing file URIs in lister output

For a given package, the debian lister generates a dictionary mapping
distribution and version to a list of files to be processed by the
debian loader.

For each file to process, the debian loader expects to find an URI
in order to download it and then use its content to ingest package
source code into the archive.

However, it turns out these URIs were not computed by the lister
in its current implementation making any debian loading task fail
due to these missing info.

So add the computation of these URIS and ensure they will be provided
in the debian loader input parameters.

Related to T2400