ONNX spec:
"kernel_shape : list of ints
The shape of the convolution kernel. If not present, should be
inferred from input W."
We were taking the number of input/output feature maps into account,
which we realized we should not.
- 1D, 2D, and 3D convolutions
- conversion to MLIR is supported only for 2D convolution
- not full support yet: still limitations on group and other params