Auto merge of #111803 - scottmcm:simple-swap-alternative, r=Mark-Simulacrum

Tweak the threshold for chunked swapping

Thanks to `@AngelicosPhosphoros` for the tests here, which I copied from #98892.

This is an experiment as a simple alternative to that PR that just tweaks the existing threshold, since that PR showed that 3×Align (like `String`) currently doesn't work as well as it could.

Author: bors