[quant] Add _FusedModule type to capture all fused modules for quantization (#47484)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/47484
Test Plan: Imported from OSS
Reviewed By: z-a-f
Differential Revision: D24774703
fbshipit-source-id: f0efc5d77035b9854ec3e31a1d34f05d5680bc22
