Reactive data diff impact analysis similar to the change categorizer in sqlmesh ui plan mode

I really love how the plan mode reacts to my code changes. It'd be helpful to have a data diff mode that reacts accordingly as those heuristics and row-level diffs in the UI help make sure users are developing in the right direction. 

The UX/UI is already there, just need to auto-populate the join key based on `grain` in the model config and have it hot reload as an option