[llvm] Reland "[LoopVectorizer] Add support for partial reductions" (PR #120721)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-cmake-x86_64-avx512-win` running on `avx512-intel64-win` while building `llvm` at step 4 "cmake stage 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/81/builds/3342

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 4 (cmake stage 1) failure: 'cmake -G ...' (failure)
'cmake' is not recognized as an internal or external command,
operable program or batch file.

```

</details>

https://github.com/llvm/llvm-project/pull/120721