[LoopVectorize] Ensure the VPReductionRecipe is placed after all it's inputs

When vectorising ordered reductions we call a function
LoopVectorizationPlanner::adjustRecipesForReductions to replace the
existing VPWidenRecipe for the fadd instruction with a new
VPReductionRecipe. We attempt to insert the new recipe in the same
place, but this is wrong because createBlockInMask may have
generated new recipes that VPReductionRecipe now depends upon. I
have changed the insertion code to append the recipe to the
VPBasicBlock instead.

Added a new RUN with tail-folding enabled to the existing test:

  Transforms/LoopVectorize/AArch64/scalable-strict-fadd.ll

Differential Revision: https://reviews.llvm.org/D129550