Implement C++ ModuleDict (#47707)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47707
Fixes #45896
Test Plan: Imported from OSS
Reviewed By: glaringlee
Differential Revision: D24872641
Pulled By: ejguan
fbshipit-source-id: 3d1dc9148ba3bcf66ab9c44ddb5774060bbc365d
