[complex] Complex support for masked_scatter and autograd support for masked_scatter and masked_select (#51281)
Summary:
Reference: https://github.com/pytorch/pytorch/issues/33152
Changes
* Enable complex support for masked_scatter
* Enable half support for masked_scatter CPU
* Enable complex autograd support for masked_scatter CPU and masked_select (both CPU and CUDA).
**Note**:
Complex Support for masked_scatter CUDA is disabled as it depends on `masked_fill` which is yet to be ported to ATen.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51281
Reviewed By: ailzhang
Differential Revision: D26127561
Pulled By: anjali411
fbshipit-source-id: 6284926b934942213c5dfc24b5bcc8538d0231af
