Tests can fail if randomly generated filenames contain underscores and frequency strings

Temporary filenames are created randomly. If such a name contains underscores and a frequency identifier then dmt_app.tests.test_ingest_dataset.TestIngestion.test_ingestion_netcdf_only can fail. It can be fixed by rerunning. Ideally the random filename should be checked for such frequency strings to avoid this happening.

Start with dmt_app.tests.test_ingest_dataset.TestIngestion.test_ingestion_netcdf_only and trace how its temporary filenames are generated. Reproduce the failure with an underscore and frequency identifier in the random name, then ensure such names are avoided and confirm the test passes without rerunning.

Written by the indexing model from the issue text.