[SCEVExpander] Migrate costAndCollectOperands to use InstructionCost.

This patch changes costAndCollectOperands to use InstructionCost for
accumulated cost values.

isHighCostExpansion will return true if the cost has exceeded the budget.

Reviewed By: CarolineConcatto, ctetreau

Differential Revision: https://reviews.llvm.org/D92238