Memoize parseIR calls in graph mode quantization
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/30188
Test Plan: Imported from OSS
Differential Revision: D18625743
Pulled By: jamesr66a
fbshipit-source-id: 88f9da8e79324ba91e3550a8fc1a05e85bb83a86
