[clang] [llvm] [HLSL] Reapply Move length support out of the DirectX Backend (#121611) (PR #122337)

[Farzon Lotfi via llvm-commits]

farzonl wrote:

@llvm-beanz  I'm really confused what is going on here
The length test case passes in the github action: https://github.com/llvm/llvm-project/actions/runs/12699150463?pr=122337
It passes locally on:

1. MacOS Intel (Intel(R) Core(TM) i9-8950HK CPU @ 2.90GHz)
2. MacOS Apple M3 Max 12 core
3. Ubuntu 22.04 AMD Ryzen Threadripper PRO 5975WX 32-Cores
4. Windows AMD Ryzen 9 5900X

BUT its failing in buildkite and on other llvm builders. I'm not sure what could do this.
https://buildkite.com/llvm-project/github-pull-requests/builds/135222

https://github.com/llvm/llvm-project/pull/122337