Unit test hpandas dassert_is_days

[sonaalKant]

Lets test the method to show all assert cases are caught.

https://github.com/kaizen-ai/kaizenflow/blob/bc8bf878faa174a77c5d23fe7976de7307b1d717/helpers/hpandas.py#L72

Steps:

1. Create multiple mock inputs and verify that all the dassert catches the invalid inputs correctly.
2. Follow the DRY principle to avoid writing repeated code. FYI @samarth9008