AddConstant and findConstant for ClassType (#29217)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29217
We want to preserve constant information in ClassType so that
users can access the constants in the module by name.
This is also used later for freezing some attribute(converting
attributes to constant)
Test Plan:
tbd
Imported from OSS
Differential Revision: D18799955
fbshipit-source-id: fbfbcd5d3f7f560368b96e2a87e270c822a3d03a
