[VPlan] Fix in-loop reduction chains using VPlan def-use chains (NFCI)

Update adjustRecipesForReductions to directly use the VPlan def-use
chains for in-loop reductions to collect the reduction operations that
need adjusting.

This allows the removal of
 * ReductionChainMap
 * recording of recipes for instruction in the reduction chain
 * removes late uses of getVPValue
 * removes to need for removeVPValueFor.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D155845