[llvm] [DirectX] Allow vector Allocas to be transformed into arrays (PR #145972)

[Farzon Lotfi via llvm-commits]

farzonl wrote:

> `tools/dxil-dis/shuffle.ll` test seems to indicate we don't want to scalarize vector allocas. This pr might need to be modified to drop the vector transformation to arrays and just keep the array recursion.

Test needed to be update to avoid the Data scalarizer pass.

https://github.com/llvm/llvm-project/pull/145972