PERF: Improve drop_duplicates for bool columns (#12963)
 - [x] closes #12963
 - [x] tests passed
 - [x] passes ``git diff upstream/master | flake8 --diff``
 - [x] whatsnew entry

Converts `bool` columns to `int` when calling `drop_duplicates()` so the factorization does not go down the `object` path.
 
```
      before           after         ratio
     [9ab57dc5]       [4b05fccb]
-     10.2±0.01ms      4.68±0.01ms     0.46  reindex.Duplicates.time_frame_drop_dups_bool

SOME BENCHMARKS HAVE CHANGED SIGNIFICANTLY.
```
