conv2d: require bias to have the same dtype as input and weight on cpu (#83686)
Fixes https://github.com/pytorch/pytorch/issues/83505
BC-breaking message:
- Previously we only required input and weight to have the same dtype on cpu (when input is non-complex). After this change, the dtype of bias is now also expected to have the same dtype. This change was necessary to improve the error message for certain combinations of inputs. This behavior now also matches that of convolution on cuda.
<details>
<summary>
Old plan
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Previously convolution (at least for slow_conv2d) did not perform type promotion, i.e. the output of `conv(int, int, float)` is an int, and that leads to the autograd assert.
This PR adds type promotion handling at the `at::native::conv2d` (this is a composite) level. We also need to correct or remove many tests that assume that conv errors when input types are mixed
Pros:
- Doing type promotion at this level avoids the complex path from having any special handling for mixed dtypes, and can potentially speed up mixed dtype inputs to now dispatch to faster kernels which are only capable of handling floats.
Cons:
- Doing type promotion at this level has the risk of introducing extra overhead when we would've dispatched to a kernel capable of handle mixed type anyway. I don't know if any of these exist at all though - it is possible that inputs with any non-float arguments are dispatched to the slow path.
If this approach is OK, we can proceed with the other convolutions as well:
</details>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/83686
Approved by: https://github.com/ngimel
