[llvm] [VFABI] Add support for vector functions that return struct types (PR #119000)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

> Is this only used by transforms or analysis also? It might be better placed as either transform or analysis utils, instead of in IR?

It's a circular dependency to place the helpers in transform or analysis as both of those depend on core. 



https://github.com/llvm/llvm-project/pull/119000