[JIT] Add API for ignoring arbitrary module attributes (#45262)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45262
**Summary**
This commit adds an API for ignoring arbitrary module attributes during
scripting. A class attribute named `ignored_attributes` containing names
of attributes to ignore can be added to the class of the instance being
scripted. Attributes ignored in this fashion cannot be used in
`forward`, methods used by `forward` or by `exported` methods. They
are, however, copied to the `RecursiveScriptModule` wrapper and can be
used by `ignored` methods and regular Python code.
**Test Plan**
This commit adds unit tests to `TestScriptPy3` to test this new API.
Test Plan: Imported from OSS
Reviewed By: eellison
Differential Revision: D23971882
Pulled By: SplitInfinity
fbshipit-source-id: 8c81fb415fde7b78aa2f87e5d83a477e876a7cc3
