[llvm] [Verifier] Prevent insertion/extraction of scalable vectors into/from fixed vectors (PR #215647)

[Sean Clarke via llvm-commits]

xarkenz wrote:

I'm not sure if there's a good way to try and prevent such intrinsics from being constructed in the first place. The best I can think of right now is to add asserts to `IRBuilderBase::Create{Insert,Extract}Vector`, but that seems awkward.

https://github.com/llvm/llvm-project/pull/215647