Add new %ansible_collection_filelist macro
    
    %ansible_collection_files cannot be adapted to dynamically determine the
    collection namespace. We need to use a file list for that.
    %ansible_collection_install writes out a file list to
    %ansible_collection_filelist. Packagers would pass
    `%{ansible_collection_filelist}` to `%files -f`.
    
    Eventually, I'd like to deprecate %ansible_collection_files. That won't
    happen until the new approach has gotten more testing and adoption.