Get SchemaCheckMode to error on ops that return inputs directly. Expose as a dynamo backend, eager_debug (#99744)
Talked to @zou3519 and @ezyang on what the right UX is: tentatively, adding a new dynamo backend is cheap and simple, so it seems worth doing. And longer term, we agreed (?) that it's worth seeing if we can get custom ops sanity asserts to run more automatically, instead of needing a separate backend.
Side comment: that actually seems tough: the mode detects secret mutations by cloning every input to every op, running the op, and checking that the data matches between the real input and the cloned input. So I doubt we'll be able to make that behavior always-on? It would need some config at least.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99744
Approved by: https://github.com/albanD, https://github.com/ezyang, https://github.com/zou3519
