Jst/add groupwise quantization

[Jiang-Stan]

首尾层8w8f weight 不同Observer实验：

Model	config	float	MinMax	MSE	Percentile w/ alpha=1e-3	ACIQ
ResNet18	4w8f weight per-channel-symmetric	69.76%	56.91%	57.59%	58.31%	52.95%
ResNet18	4w8f weight per-group-symmetric group_size=32	69.76%	59.64%	62.08%	59.67%	52.23%
ResNet18	4w8f weight per-group-symmetric group_size=8	69.76%	66.57%	65.99%	66.57%	50.29%

feature不同Observer实验：

Model	config	float	MinMax	MSE	Percentile w/ alpha=1e-3	ACIQ
ResNet18	8w4f feature per-tensor-affine	69.76%	57.51%	67.90%	67.45%	67.71%
ResNet18	8w4f feature per-group-affine group_size=32	69.76%	60.18%	67.94%	67.49%	67.15%
ResNet18	8w4f feature per-group-affine group_size=8	69.76%	62.69%	67.68%	67.27%	65.496%