Handle rxnorm_historical where NDCs are mapped to multiple RXCUIs

[jrlegrand]

Problem Statement

Resolve the problem identified in https://github.com/coderxio/sagerx/issues/265

Criteria for Success

We have an extra 7k+ NDCs available from RxNorm Historical.

Additional Information

Maybe ensure all the RXCUIs have the same clinical ingredient and if so, pick whichever RXCUI seems most representative of the NDC, somehow?