TST: GH38718 Tests for casting an interval range from float to int
xrefs #38697 , #15832

- [x] closes #38718
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

cc @jbrockmendel  LGTM thanks @moink 