Cythonized GroupBy any

- [X] closes #15435
- [X] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] whatsnew entry

```bash

       before           after         ratio
     [2fdf1e25]       [a2223dbf]
-           1.21s          956±3ms     0.79  groupby.GroupByMethods.time_method('float', 'mad')
-         141±2ms       57.8±0.9μs     0.00  groupby.GroupByMethods.time_method('int', 'any')
-         213±7ms         56.6±1μs     0.00  groupby.GroupByMethods.time_method('float', 'any')

SOME BENCHMARKS HAVE CHANGED SIGNIFICANTLY.
```