[JIT] Add recursive scripting for class type module attributes (#55124)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55124
**Summary**
This commit modifies type inference (used by the module scripting code)
so that it tries to script the type of any class instances that it
encounters. This enables recursive, automatic scripting of class type
module attributes.
**Test Plan**
This commit adds a test case for this to `TestClassType`.
Test Plan: Imported from OSS
Reviewed By: gmagogsfm
Differential Revision: D23971883
Pulled By: SplitInfinity
fbshipit-source-id: 7a5a2e7c12ee68cbdeb0a07e6aaf98734a79cb06