[Pytorch Edge] Extend runtime compatibility to custom classes (#66972)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66972
Add api to view how many custom classes we have and what their names are
Test Plan: unit test
Reviewed By: cccclai
Differential Revision: D31811337
fbshipit-source-id: 9f8ca1fc578a0a5360c9cd8f95475acc33f250e4
