[ET-VK][qconv] Add flexible layout impl for im2col

[SS-JIA]

Stack from ghstack (oldest at bottom):

• -> [ET-VK][qconv] Add flexible layout impl for im2col #17249
• [ET-VK][qconv] Add flexible layout impl for quantized pointwise conv #17221
• [ET-VK][testing] Create dedicated test binary for pointwise convolutions #17220
• [ET-VK][qconv] Add layout-agnostic general shader for quantized conv #17219
• [ET-VK][quantization] Add layout-flexible clone for int8x4 tensors #17171
• [ET-VK][qconv] Add layout-flexible impl of quantized depthwise conv2d #17108
• [ET-VK][ez] Implement helper functions to get fastest moving dim #17107
• [ET-VK][quantization] Implement layout-flexible quantize/dequantize operators #17106
• [ET-VK] Add alignment fields to PackedDimInfo for padded size calculation #17170
• [ET-VK][testing] Add per-shader timing breakdown to benchmark output #17105

This implements an im2col-based approach for quantized conv2d, which
transforms convolution into matrix multiplication. The im2col
transformation extracts sliding windows from the input tensor and
reshapes them into a 2D matrix, enabling reuse of the optimized
pointwise convolution shader for the compute-intensive portion.

Two im2col shaders are added:

• q8ta_im2col.glsl: Generic shader with layout-agnostic input access
  via BufferMetadata and specialization constants
• q8ta_im2col_4w4c.glsl: Optimized shader for 4W4C input layout that
  exploits the alignment between consecutive width positions and packed
  channel values

The im2col output is always stored in 4W4C layout to match the expected
input format of the pointwise convolution shader. The operator is
registered as etvk.q8ta_conv2d_im2col.default and currently supports
non-grouped convolutions where input channels is a multiple of 4.

Authored with assistance from Claude.

Differential Revision: D92407723

[pytorch-bot]

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❌ 3 New Failures, 1 Pending, 3 Unrelated Failures

As of commit 6fa8b78 with merge base 1cffd23 ():

NEW FAILURES - The following jobs have failed:

• pull / unittest / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 9a703f324bd7f244f6e78ee1e9c81c66b204961e44c1595768b87b24a7ffd2ba /exec failed with exit code 1
• pull / unittest-editable / linux / linux-job (gh)
  RuntimeError: Command docker exec -t c50d4dc039c473b4d961d5eb59ac293cc293dc15fece9b3d016351a5ad0095ce /exec failed with exit code 1
• Test CUDA Builds / test-model-cuda-e2e (mistralai, Voxtral-Mini-3B-2507, quantized-int4-tile-packed) / linux-job (gh)
  RuntimeError: Command docker exec -t bf74a0421fe2aa592fb5b6155f8d8d52a65b9791aff563b8ac96f7c412dbcdd1 /exec failed with exit code 1

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-samsung-quantmodels-linux / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest / macos / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

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