[pytorch] Make qconv forward() thread safe (#63432)

[pytorch] Make qconv forward() thread safe (#63432)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63432

There's a race condition in quantized models when multiple threads call forward() due to qnnpack packing the weights the first time the operator is called. This locks the entire apply_impl function.

Test Plan:
https://github.com/pytorch/pytorch/issues/58055

Ran the script before and after, original crashes went away

Reviewed By: kimishpatel

Differential Revision: D30229520

fbshipit-source-id: d06cabe24199a80325cd57f24a7fd60624be2cf7