The TDML runner should be enhanced to allow specifying a file name for the tdml:infoset.

This is because DFDL schema projects, such as NACHA, want to be easily tested using TDML, but also want the same infoset files to be available for users treating them as examples who want to use the Daffodil CLI, or other thngs, but want to use these same test data files.

By allowing the TDML runner to reference these infosets in files we avoid having them redundantly specified in the TDML file as well as in a separate file.