Initial implementation of quantile operator (#39417)
Summary:
Implementing the quantile operator similar to [numpy.quantile](https://numpy.org/devdocs/reference/generated/numpy.quantile.html).
For this implementation I'm reducing it to existing torch operators to get free CUDA implementation. It is more efficient to implement multiple quickselect algorithm instead of sorting but this can be addressed in a future PR.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39417
Reviewed By: mruberry
Differential Revision: D22525217
Pulled By: heitorschueroff
fbshipit-source-id: 27a8bb23feee24fab7f8c228119d19edbb6cea33
