port masked_select from TH to ATen and optimize perf on CPU (#33269)
Summary:
This PR ports `masked_select` from TH to ATen and optimize the performance on CPU with TensorIterator.
https://github.com/pytorch/pytorch/issues/33053
1. single socket run: up to **5.4x** speedup;
2. single core run: up to **1.16x** speedup.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33269
Differential Revision: D20922288
Pulled By: ngimel
fbshipit-source-id: 38e183a4e3599bba29bbbebe36264026abe1c50e
