BUG: Fix Series(List[Interval]) to infer interval dtype
- [X] closes #23563
- [X] tests added / passed
- [X] passes `black pandas`
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] whatsnew entry

@jschendel can you rebase @jschendel still active? Merged master. This looks good. can you merge master;ping when green. #30640 needs to get merged before this will be good to go per https://github.com/pandas-dev/pandas/issues/23563#issuecomment-570251929 This is green now. Anything left that I should address? lgtm. thanks @jschendel 