[ET-VK][ez] Implement helper functions to get fastest moving dim

[SS-JIA]

Stack from ghstack (oldest at bottom):

• [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

Add C++ and GLSL helpers to query the fastest moving dimension (the
dimension with stride 1 in buffer layout). This is useful for optimizing
memory access patterns in shaders, as iterating along the fastest moving
dimension maximizes cache locality.

The C++ fastest_whcn_dim() method accounts for block-transposed layouts by
returning outer_packed_dim instead of packed_dim when applicable. A
corresponding GLSL macro extracts this info from the hashed layout.

Differential Revision: D92061369

[pytorch-bot]

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❌ 4 New Failures, 2 Unrelated Failures

As of commit 73b4a69 with merge base 477867a ():

NEW FAILURES - The following jobs have failed:

• pull / test-vulkan-operators-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 1b124f461e39fdeb31f56a9f0203d292da1ef6b6b2820e53ad2c0d24687684bb /exec failed with exit code 134
• pull / unittest-editable / macos / macos-job (gh)
  export/tests/test_target_recipes.py::TestTargetRecipes::test_linear_model
• Test CUDA Builds / export-model-cuda-artifact (openai, whisper-large-v3-turbo, quantized-int4-weight-only) / linux-job (gh)
  RuntimeError: Command docker exec -t 4a7130e2bed0948e0bf15b770bf9b32e6d3fcc85fe980caf0d6336ffcbf1744a /exec failed with exit code 1
• Test CUDA Builds / export-model-cuda-artifact (openai, whisper-small, non-quantized) / linux-job (gh)
  RuntimeError: Command docker exec -t 7a963a0d840194a5f1bfa4a53e0699166d7bf561a45f951196934719f8972044 /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-models-linux / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / test-samsung-quantmodels-linux / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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