Merge all vec256 tests into one framework (#47294)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/47294
Test Plan: Imported from OSS
Reviewed By: H-Huang
Differential Revision: D24707378
Pulled By: glaringlee
fbshipit-source-id: cc47ddb49bc2a3ecff9359e9623b0d7774743398
