Add GPTQ quantization to executorch (not tested) (#2274)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/2274

will test in OSS and fix issues in a separate PR

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Reviewed By: digantdesai

Differential Revision: D54569842

fbshipit-source-id: 7c3e60833d8e144cb5842842b4f640138dfa9382