DOC: resample warnings
- [ ] closes #13618, closes #13520
- [ ] tests added / passed
- [ ] passes `git diff upstream/master | flake8 --diff`
- [ ] whatsnew entry

Prevents warnings triggered by IPython by matching against `'_repr'` or `'_ipython'`, and expands the `resample` warning message to indicate what caused the deferred object to be materialized.
