[llvm] [llvm] Ensure propagated constants in the vtable are aligned (PR #136630)

[via llvm-commits]

PiJoules wrote:

> yes, if possible. That way, when you update the test in this PR, it will be easy to understand what's changing in the new cases.

Uhh is there a way I can upload only the diff between this PR and https://github.com/llvm/llvm-project/pull/138989/ in this PR rather than having 2 commits? Locally what I have is 

```
6f08bc78bce0 (HEAD -> wpd-alignment, committing/wpd-alignment) [llvm] Ensure propagated constants in the vtable are aligned
0a8b2cf472e7 (committing/wpd-alignment-precommit-tests, wpd-alignment-precommit-tests) [NFC][WPD] Add constant propagation tests to account for relative vtables
```

and I assumed pushing the branch for this PR would only push the that commit rather than both commits.

https://github.com/llvm/llvm-project/pull/136630