update eval for group_gem

[msaroufim]

nvfp4_group_gemm is a grouped matrix multiplication. Each test case processes multiple GEMMs simultaneously, where m, n, k are lists specifying the dimensions for each group:

• {"m": [96, 128], "n": [128, 256], "k": [128, 512], "g": 2, "seed": 1111}

This means:

• Group 0: M=96, N=128, K=128
• Group 1: M=128, N=256, K=512