.csv support for Whodrug

currently only .txt files are supported for whodrug.

We will need to make changes to the terms_factory as well as the data_services that reads the files.
https://github.com/cdisc-org/cdisc-rules-engine/tree/main/cdisc_rules_engine/models/dictionaries/whodrug

AC:
update data service to accept and read CSV
whodrug factory should populate cache with this read CSV data
ensure txt/csv whodrug checks work similarly after the files are parsed and cached.

Start in cdisc_rules_engine/models/dictionaries/whodrug and inspect the terms_factory and data_services mentioned in the issue. Trace how .txt files are read and cached, then verify that CSV input populates the same cache and that both TXT and CSV Whodrug checks behave equivalently after parsing.

Written by the indexing model from the issue text.