[RTADPA BW Tests] Use new exp24 minbias for AllenInMoore_Hlt1_Bandwidth test

Standalone, is required by: lhcb-datapkg/PRConfig!358 (merged)

Updates Hlt1Conf/tests/options/bandwidth option files from the previous 'stand-in' input to the exp24 minbias.
Changes download_mdfs to instead be a wrapper of download_files, to allow addition of download_digis with little/no duplication.

Pending developments in PRConfig, this is ready.