[Static Runtime] Implement aten::cumsum out variant (#64159)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/64159
Test Plan:
Confirm out variant is called for both versions:
```
> buck run //caffe2/benchmarks/static_runtime:static_runtime_cpptest -- --v=1
```
Reviewed By: mikeiovine
Differential Revision: D30622819
fbshipit-source-id: a2c8c7f969dae5f507718fb3d513e1fb4f026736
