[quant][graphmode][fx][test] Add test for nn.Sequential (#47411)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/47411
Test Plan: Imported from OSS
Reviewed By: supriyar
Differential Revision: D24745678
fbshipit-source-id: f8a4858748402db6e72a21bf051f5542b9215ffa
