[llvm] [SelectionDAG] Use unaligned store to move AVX registers onto stack for `extractelement` (PR #78422)

[Danila Malyutin via llvm-commits]

danilaml wrote:

Can you make a follow up PR that fixes similar issue in ExpandInsertToVectorThroughStack (and possibly ExpandVectorBuildThroughStack, although I don't have a test for that).

https://github.com/llvm/llvm-project/pull/78422