[llvm] [LV] Add vector library call legalization via VPlan transform (PR #197661)

[via llvm-commits]

Andarwinux wrote:

> the vectorizer today either emits an unsupported call (forcing backend scalarization) or falls back to scalar calls outright.

https://github.com/llvm/llvm-project/issues/138171
https://github.com/llvm/llvm-project/issues/162239
https://github.com/llvm/llvm-project/issues/164642

Actually will cause miscompilation.

https://github.com/llvm/llvm-project/pull/197661