[llvm] LoopVectorize: Set branch_weight for conditional branches (PR #72450)

[Matthias Braun via llvm-commits]

MatzeB wrote:

This was already reviewed and accepted https://reviews.llvm.org/D159322 under the condition that `setBranchWeights` is factored out which I did now.

https://github.com/llvm/llvm-project/pull/72450