ONNX MatMulInteger support

[GregoryMorse]

Describe the feature request

The ONNX specification since opset 10 has specified a MatMulInteger operation which allows uint8/int8 types among other things. MatMul specifically does not allow this size.

Currently only MatMul is support, and uint8/int8 will fail to compile per the ONNX spec on that operation.

Describe scenario use case

Any places where small integer arithmetic is used, specifically when computing matrix multiplication with uint8/int8 matrix x uint8/int8 matrix -> int32 matrix.

[fatcat-z]

Close this issue since the PR has been merged. Feel free to reopen it if necessary.