[PyTorch] MHA: add test for transform_bias_rescale_qkv (#72464)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/72464
We had some trouble getting this component (and this test!) right, so let's test it.
ghstack-source-id: 149201478
Test Plan: new test passes
Reviewed By: zrphercule
Differential Revision: D33992477
fbshipit-source-id: cc377eed5d4a4412b42bdabf360601c6e52947cf
(cherry picked from commit 9832867b12e555b512ded16decbea17b1794bda8)
