[static runtime] Implement aten::sign (#61154)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/61154
Test Plan:
Added `StaticRuntime.IndividualOps_Sign`
```
[djang@devvm861.prn0 ~/local/fbsource/fbcode/caffe2] buck run //caffe2/benchmarks/static_runtime:static_runtime_cpptest -- -v 1
...
[ RUN ] StaticRuntime.IndividualOps_Sign
V0701 12:05:31.836099 3679080 impl.cpp:455] StaticModuleOptions: cleanup_activations 1, enable_out_variant 1, optimize_memory1, optimize_graph_output_memory0
V0701 12:05:31.898192 3679080 impl.cpp:1279] Switch to out variant for node: %3 : Tensor = aten::sign(%input.1)
V0701 12:05:31.898849 3679080 impl.cpp:1279] Switch to out variant for node: %4 : Tensor = aten::clone(%3, %2)
```
Reviewed By: hlu1
Differential Revision: D29518603
fbshipit-source-id: e47b96d037fea639c41052f3849c82bbfa5f482a
