hexagon: add Q4_1 support to MUL_MAT

[max-krasnyansky]

Add support for Q4_1 data type for MUL_MAT ops in the Hexagon backend.

• Add support for repacking Q4_1 into Q4_1x4x2.
• Add support for vec_dot_1x1,2x1,2x2 kernels.
• Update matmul_2d code to handle src0 in Q4_1x4x2.
• Update supported MUL_MAT types.
• Fix dot product kernels for Q4_1x4x2 format.
• Add HMX dequantization logic for Q4_1.

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PR created automatically by Jules for task 120578630328963272 started by @max-krasnyansky

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