add Quantizer support to IValue (#42438)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/42438
Test Plan: Imported from OSS
Reviewed By: smessmer
Differential Revision: D22894190
Pulled By: bhosmer
fbshipit-source-id: b2d08abd6f582f29daa6cc7ebf05bb1a99f7514b
