[ProfCheck] Add prof data for lowering of @llvm.cond.loop
When there is no target-specific lowering of @llvm.cond.loop, it is
lowered into a simple loop by PreISelIntrinsicLowering. Mark the branch
weights into the no-return loop as unknown given we do not have value
metadata to fix the profcheck test for this feature.
Reviewers: mtrofin, alanzhao1, snehasish, pcc
Pull Request: https://github.com/llvm/llvm-project/pull/180390
