[PyTorch] Split StaticModule out of test_static_runtime (#121028)
I want to use StaticModule in another (internal) test, so splitting it out.
Differential Revision: [D54384817](https://our.internmc.facebook.com/intern/diff/D54384817/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121028
Approved by: https://github.com/suo
