Auto merge of #60162 - gnzlbg:uss, r=alexcrichton

Breaking update of stdsimd

This commit updates stdsimd and contains two breaking changes:

* https://github.com/rust-lang-nursery/stdsimd/pull/733
* https://github.com/rust-lang-nursery/stdsimd/pull/586

We already did a crater run of 586 but we should do another one here.

r? @alexcrichton

stdsimd @ 4bf456c3

-Subproject commit 45f8450916f85149ed3b1df8188b2441601a2c8a
+Subproject commit 4bf456c35e85fcca5cf95008401af8ab25abf850