[Quant] Bug fix (#107899)
Summary:
When two layers are quantized differently, observer map update updates
map for key (observed_node, node), whereas it should really be
(original_input, node)
Test Plan:
Test in the next diff adds a test where it otherwise fails
Reviewers:
Subscribers:
Tasks:
Tags:
Differential Revision: [D48663145](https://our.internmc.facebook.com/intern/diff/D48663145)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107899
Approved by: https://github.com/jerryzh168
ghstack dependencies: #107105, #107106
