[llvm] [LV] Add support for uniform parameters on vectorized function variants (PR #72891)

[Graham Hunter via llvm-commits]

huntergr-arm wrote:

Rebased on top of b1fba568f6d4d824554fa22f43ec0f689a265664 and adjusted ISA name to 's' for scalable vector tests. Added a case where the uniform parameter has a smaller element  type than the vector parameter.

https://github.com/llvm/llvm-project/pull/72891