[FEA] df.explode with multiple columns

**Is your feature request related to a problem? Please describe.**
Pandas supports exploding multiple columns with `df.explode`, but currently cudf fails for that case.

**Describe the solution you'd like**
Support explode with multiple column names. The doc contains an example of the expected output from a multi column explode:
https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.explode.html#pandas-dataframe-explode

**Describe alternatives you've considered**
I haven't been able to come up with a workaround to this, but it might be 2 separate explodes + a merge of some kind to get to the same result.

**Additional context**
Add any other context, code examples, or references to existing implementations about the feature request here.