[ET-VK] Fix mixed-dtype binary ops and comparison op padding bugs

[SS-JIA]

Stack from ghstack (oldest at bottom):

• [ET-VK] Insert prepack nodes for constant primary inputs of prepacking ops #17850
• -> [ET-VK] Fix mixed-dtype binary ops and comparison op padding bugs #17849
• [ET-VK] Fix softmax NaN and depthwise conv correctness bugs #17848

Two bugs caused incorrect outputs in models with mixed-dtype binary operations
(e.g. EdgeTAM remaining frames):

1. Mixed-dtype binary ops (e.g. int arange vs float tensor) were fed to shaders
   that declare both inputs with the same DTYPE, causing data misinterpretation.
   This is now fixed by adding an InsertDtypePromotionPass export pass that
   inserts _to_copy nodes to promote inputs to a common dtype at compile time.
   The _to_copy op is extended to support int<->float conversions via new
   view_convert_texture shaders, and the previous float/half-only restriction
   in ToCopy.cpp is replaced with branching logic that uses BlitNode for
   same-dtype/float<->half and view_convert shaders for other conversions.

2. Texture3d comparison operators (gt, lt, le, ge, eq) used all() to reduce
   component-wise bvec4 results to a single bool. With packed textures where
   padding components are zero, all() always returned false because padding
   zeros fail comparison against non-zero values. Fixed by removing all() so
   the result stays as a component-wise bvec4, which is correctly converted to
   uvec4 for the Bool output texture.

Additional changes:

• New view_convert_texture.glsl shader and YAML for texture dtype conversion
• add_view_copy_convert_texture_node added to View.cpp/h
• _to_copy op registry updated to accept int dtypes (FP_INT_T)

Differential Revision: D95217948

[pytorch-bot]

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❌ 1 New Failure, 4 Unrelated Failures

As of commit bb093ef with merge base 1a75394 ():

NEW FAILURE - The following job has failed:

• Build Presets / apple (ios-simulator) / build (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script 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 / unittest / macos / macos-job (gh) (trunk failure)
  AttributeError: '_OpNamespace' 'mkldnn' object has no attribute '_is_mkldnn_acl_supported'
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  AttributeError: '_OpNamespace' 'mkldnn' object has no attribute '_is_mkldnn_acl_supported'
• Test CUDA Windows Export and E2E / test-model-cuda-windows-e2e (mistralai, Voxtral-Mini-3B-2507, non-quantized) / windows-job (gh) (trunk failure)
  Process completed with exit code 1.
• Test CUDA Windows Export and E2E / test-model-cuda-windows-e2e (mistralai, Voxtral-Mini-3B-2507, quantized-int4-weight-only) / windows-job (gh) (trunk failure)
  Process completed with exit code 1.

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