[ET-VK][q8ta] Add q8ta_linear operator for int8 quantized linear

[SS-JIA]

Stack from ghstack (oldest at bottom):

• [ET-VK][ez][qconv] Add auto-selection to prefer im2col for q8ta_conv2d #17568
• [ET-VK][q8ta] Fix addmm arg indexing in QuantizedLinearMatch #17567
• [ET-VK][q8ta] Add q8ta_linear_gemv op for batch-1 int8 linear #17566
• -> [ET-VK][q8ta] Add q8ta_linear operator for int8 quantized linear #17565
• [ET-VK][export] Update tensor representation sync logic to allow for flexibility in memory layouts #17564
• [ET-VK] Support different input layouts in q8ta_binary operator #17563
• [ET-VK][ez] Always partition batch norm as it will be fused #17508
• [ET-VK] Add fused q8ta_relu unary operator for int8x4 tensors #17507
• [ET-VK][qconv] Add apply_relu support to q8ta conv operators #17506
• [ET-VK][qconv] Pad weight_sums buffer to multiple-of-4 alignment #17505
• [ET-VK][qconv] Fix depthwise weight_sums sum dimension #17504

Add a new q8ta_linear operator that performs fully quantized int8
linear (matmul + bias) with per-tensor activation quantization and
per-channel weight quantization, producing int8 output. This enables
back-to-back quantized linear layers without intermediate
dequantize/quantize steps.

The operator reuses the existing tiled int8 linear GLSL headers
(input/weight tile loading, int8 dot product accumulation, weight
scales/sums/bias loading) and adds output quantization via
quantize_and_pack to produce packed int8 output.

The fusion pass in quantized_linear.py detects the
q→dq→linear→q pattern (where the output quantize node comes from a
subsequent quantized op's input) and fuses it into a single
q8ta_linear call.

This diff was authored with Claude.

Differential Revision: D93768642

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❌ 4 New Failures

As of commit 3a94e2e with merge base 7b843e4 ():

NEW FAILURES - The following jobs have failed:

• pull / android / run-emulator (gh)
  The process '/opt/android/sdk/platform-tools/adb' failed with exit code 224
• pull / test-openvino-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 64a9af1b51d6cd215752b89e914faef2a28eae7401faafc04e2b70d754aa49b4 /exec failed with exit code 1
• pull / test-vulkan-operators-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 5084322794c49ddac8f6e05b670df7cbe14fecd8ad57057e26135c050f8b25d5 /exec failed with exit code 139
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t f3f05c0c1b25ebc7ba57b5dac2ee874ec50d9624788cc60925502e41e8f37d00 /exec failed with exit code 1

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