[torch] Use __prepare_scriptable__ for closures (#121553)
Summary:
This fixes a case left incomplete by https://github.com/pytorch/pytorch/pull/106229
The object is using __prepare_scriptable__ correctly inside of torch.jit.script()
but the clousre that is obtained below is using the non-prepared version.
This causes issues when the prepared and non-prepared versions are in different python modules.
Test Plan:
```
buck2 run mode/opt caffe2/test:jit -- -r test_decorator
```
Differential Revision: D54308741
Re-exporting, as #120806 #121307 were not properly merged.
Co-authored-by: Daniel Herrera <dherrera@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121553
Approved by: https://github.com/huydhn, https://github.com/seemethere
