This patch moves the logic that computes the instruction latency from a scheduling class descriptor into MCSchedModel from TargetSchedModel.
The TargetSchedModel API is unchanged; now method TargetSchedModel::computeInstrLatency(const MCSchedClassDesc &) simply delegates the latency computation to MCSchedModel.
The goal is to make the latency information accessible through the MCSchedModel interface.
This is particularly important for tools (for example: llvm-mca), that have access to MCSchedModel, but not TargetSchedModel.
This is a first step towards fixing PR36676.
No functional change intended.