refactor: decide between loadDICOMSITK and read_dicom_series

[jjjermiah]

So I know I have this function and I used it in example.ipynb, but the actual pipeline uses the read_dicom_series function from med-imagetools. I feel like we should discuss what to do with the loadDICOMSITK function. I feel like we can either:

1. Get rid of it and just use read_dicom_series everywhere
2. Call read_dicom_series in loadDICOMSITK like how we call the MIT functions in loadRTSTRUCTSITK to load the RTSTRUCT

Thoughts?

Originally posted by @strixy16 in #81 (comment)