RFC: modify `col_sample_display` to better check for numeric types, this avoids bad dates casting as numeric

It helps managing 3 scenarios of testing numeric columns

• date-cols which can be converted to seconds since epoch numbers ❎
• numbers in string dtype ✔
• proper numbers ✔

Also, given the to_numeric operation inside the func that was modifying a single column. Now a copy of that column is used internally in the func.