[extension/llm] IOManager interface

[JacobSzwejbka]

🚀 The feature, motivation and pitch

Certain backends like qnn or coreML utilize static attention which requires very special handling in the runner code. At a higher level different algorithms in general can cause minor differences in the IO of the model that make it difficult for the runner class to handle causing folks to have to fork the runner for every new model.

An IOManager interface would simplify the runner code abstracting away minutia that really boils down to state management away letting a lot of the other runner boilerplate to be shared

Alternatives

No response

Additional context

No response

RFC (Optional)

No response