[NFCI] Move cost estimation from TargetLowering to TargetTransformInfo.

TragetLowering had two last InstructionCost related `getTypeLegalizationCost()`
and `getScalingFactorCost()` members, but all other costs are processed in TTI.

E.g. it is not comfortable to use other TTI members in these two functions
overrided in a target.

Minor refactoring: `getTypeLegalizationCost()` now doesn't need DataLayout
parameter - it was always passed from TTI.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D117723