Create minimal realistic ONNX networks for testing

[avikde]

• XOR solver
• Something interesting with Gemm?

[avikde]

MNIST https://huggingface.co/onnxmodelzoo/mnist-12-int8 uses these, which is a lot to implement, so I may have to find something simpler but realistic.

[avikde]

• Simple MatMul
• Read Kung again to see about PEs
• Evaluate if the pe.sv can do multiply and add in few steps