ENH: Add public start, stop, and step attributes to RangeIndex
- [X] closes #25710
- [X] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] whatsnew entry

Comments:
- Was originally going to add the tests for this to `test_constructor` but decided to create a new test instead. I parametrized `test_constructor` to clean it up before deciding to create a separate test and kept those changes in the PR.
- Copied the `start`/`stop`/`step` docstrings from the Python docs for `range` with a small rewording to fit it on one line