[Feature Request] Add more unary operators

[george-qi]

As shown in the comments here:

https://github.com/pytorch/maskedtensor/blob/a674e87cd4ee541e7a63c31b967c64d5bff433db/maskedtensor/unary.py#L79-L103

we have a number of unary operators that are not yet supported, possibly due to missing codegen or complex semantics. Opening this issue as a feature request to have these added