[quant][fx][graphmode][api] Change API for custom module (#45920)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45920
See docs for new way of defining custom modules
Test Plan: Imported from OSS
Reviewed By: vkuzo
Differential Revision: D24145856
fbshipit-source-id: 488673fba503e39e8e303ed5a776fe36899ea4e3
