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

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

Bike-shedding I know plus I've not had anything to do with this PR so don't intend to hold it up but is it possible to come up with a better name than VectorUtils?

The name is already in use and from what I can see the functionality of the new one has little to do with vectors other than VactorType. Perhaps `VectorTypeUtils`?

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