Allow per-channel quantization without specifying quantization dimension
Allow per-channel quantization without specifying quantization dimension

Current QuantizedType in QuantizationConfig can only specify per-channel quantization with specified quantization dimension. But quantization dimension may vary depending on the dimension layout within a model, but at the same time, it is straight forward to decide quantization dimension for the most of the times(output feature dimension for convolution, and non-batching and non-contracting dimension for dot_general - usually it is unique for ODML cases). Therefore, allowing option to do per-channel quantization without specifying quantization dimension will make it more accessible.
