parsed_to_cn_var should support total_copies ranges

This accounts for a pretty small number of variations in ClinVar, but there are some. I think there are 14, all with only 1 submission.

One example:
https://www.ncbi.nlm.nih.gov/clinvar/variation/1048551/

https://vrs.ga4gh.org/en/stable/terms_and_model.html#copynumbercount

The arguments we would use for the above would be:
```json
{
"assembly": "GRCh37",
"chr": "10",
"start": 131243689,
"end": 132131959,
"total_copies": [3, 4]
}
```