[TorchScript] Support user defined classes as constants (#5062)
Summary:
Pull Request resolved: https://github.com/pytorch/glow/pull/5062
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45556
User defined classes can be used as constants. This is useful when freezing and removing the module from the graph.
Test Plan: waitforsadcastle
Reviewed By: eellison
Differential Revision: D23994974
fbshipit-source-id: 5b4a5c91158aa7f22df39d71f2658afce1d29317
