[SR] Relax aten::__is__ constraint for SR enablement (#71807)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71807
There's no need to completely disallow `aten::__is__` and `aten::__isnot__`. The only problematic case is when the comparison is between two tensors, e.g. in
```
def forward(x):
y = x.detach()
# Should be false, but we get True
# after our EliminateNoOps pass
return x is y
```
Test Plan: New unit test covers this case
Reviewed By: d1jang
Differential Revision: D33783668
fbshipit-source-id: c9f57fa96937ecce38a21554f12b69c45cc58fe4
(cherry picked from commit 019588f4ca3fcd2b3ae51bccab102f0538745b15)
