[VPlan] Don't use Ingredient to get type in VPWidenMemoryRecipe (NFC) (#200049)
The scalar load/store type is already available on the recipe: load
recipes inherit from VPSingleDefRecipe and expose it via
getScalarType(); store recipes can derive it from the stored value's
type via VPTypeAnalysis.
This migrates a number of lookups to be based on information already
available in VPlan directly.