[Aimodel] Enable ppss control for weight_recent, balance_classes, calibrate_probs

[trentmc]

We recently updated Aimodel.py where it would

1. reweight the most recent sample by 10x, and second-most-recent by 5x
2. always balance classes
3. always calibrate probabilities

But it's not clear which helps, or not. We need to be able to test these better without hacking things on and off.

Ideally we can also add new techniques to solve a given problem.

How: add control for (1)(2)(3) to ppss.yaml, specifically ai_model_ss.