[QNN EP] Support quantized BatchNorm with per-channel DQ params on QNN HTP

[qti-yuduo]

Motivation:

QNN HTP was rejecting quantized BatchNorm models where parameters (scale, mean, var) come through DequantizeLinear nodes with per-channel INT8 quantization. This pattern is common in quantized models from quantization tools.

Changes:

• Helpers to resolve BatchNorm params through DQ nodes to their underlying initializers
• Support per-channel dequantization for BatchNorm parameters
• Support input datatype of UFIXED_POINT_16
• Add unit test covering this QDQ params configuration