[quant][graphmode][fx][fusion] Add test for fuse_fx (#47085)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47085
Both in train and eval mode
Test Plan: Imported from OSS
Reviewed By: vkuzo
Differential Revision: D24632457
fbshipit-source-id: 486aee4e073fb87e9da46a344e8dc77e848a60cf
