Auto tune register selection heuristics

[kunalspathak]

As part of #43318, lot of experiments were performed to analyze the optimal ordering of register selection heuristics. As a continued effort, implement an auto-tuning framework which would pick the right ordering based on the method for which register allocation is happening.

category:cq
theme:register-allocator
skill-level:expert
cost:medium
impact:medium

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.