model card: int8 is measured now, drop the stale 'not characterised' caveat

add FP32 + int8 ONNX graphs and int8 results (int8 is free at every sparsity level)

NSNet2 under semi-structured sparsity: 2:4, 4:8, 1:4, 1x4:80, unstructured:80 + dense control