BUG: `DataFrame.resample` changing index type to `MultiIndex` when dataframe is empty and upsampling
- [x] Closes #55572
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests)
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit)
- [x] Added an entry in the latest `doc/source/whatsnew/v2.1.3.rst` file

@mroeschke Changelog updated. @mroeschke Sorry for the delay. Changelog updated now. So sorry this keeps getting missed. Could you please the whatsnew note to `2.2.1.rst`? I can merge as soon as that's made Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.