Summary:
- Rename `invariantModels` to `purityModels`
- Track which arguments are modified in purity models. Before we were invalidating all arguments of impure modeled functions. Instead, now we only invalidate modified args given in the model. This should ideally result in more precision in the analysis.
- Add some more purity models for :`cast`, `new`, `new_array` and `Math.random`
Reviewed By: mbouaziz
Differential Revision: D15535332
fbshipit-source-id: 5395800d9