 Add benchmark for indexing with .loc for sorted/unsorted DatetimeIndex
- [x] closes #38690 
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

@mroeschke Hi The testing pipeline in green. Thank for review. @mroeschke Pipeline check in green Thanks for following up @weikhor 