refactor: Move scalar_types.py to sgl-kernel to avoid circular import (#8720)

sgl-kernel/tests/test_marlin_repack.py

@@ -2,8 +2,8 @@ import numpy as np
 import pytest
 import torch
 from sgl_kernel import awq_marlin_repack
+from sgl_kernel.scalar_type import scalar_types
 
-from sglang.srt.layers.quantization.scalar_type import scalar_types
 from sglang.srt.layers.quantization.utils import (
     get_pack_factor,
     pack_cols,