Add image processing utilities for HDR/SDR video preprocessing

[metascroy]

Summary:
This diff adds a new executorch.extension.vision module with image processing utilities for preprocessing and postprocessing video frames in ML pipelines.

Key features:

• Transfer functions: PQ (ST.2084), HLG (BT.2100), sRGB gamma
• Color gamut conversion: BT.2020 ↔ BT.709 matrices
• Factory methods for common pipelines: HDR10→linear, HLG→linear, SDR→linear, ImageNet normalization
• ImagePreprocessor and ImagePostprocessor classes that produce torch.export.ExportedProgram for on-device execution

Testing:

• Comprehensive tests validate implementations against the colour-science reference library
• Tests cover transfer function accuracy, gamut matrix correctness, and full E2E pipelines
• Added colour-science as a test dependency in both Buck (TARGETS) and OSS (pyproject.toml)
  This diff adds a new executorch.extension.vision module with image processing utilities for preprocessing and postprocessing video frames in ML pipelines.

Key features:

• Transfer functions: PQ (ST.2084), HLG (BT.2100), sRGB gamma
• Color gamut conversion: BT.2020 ↔ BT.709 matrices
• Factory methods for common pipelines: HDR10→linear, HLG→linear, SDR→linear, ImageNet normalization
• ImagePreprocessor and ImagePostprocessor classes that produce torch.export.ExportedProgram for on-device execution

Testing:

• Reference correctness tests in extension/vision/test/ validate implementations against the colour-science library
• CoreML integration tests in backends/apple/coreml/test/test_image_processing.py verify CoreML delegate matches EP output and demonstrate recommended dtype/compute precision patterns for deployment
• Added colour-science as a test dependency in both Buck (TARGETS) and OSS (pyproject.toml)

Differential Revision: D92471879

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/17269

• 📄 Preview Python docs built from this PR

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❌ 5 New Failures, 2 Unrelated Failures

As of commit e1effb7 with merge base f48a600 ():

NEW FAILURES - The following jobs have failed:

• Lint / lintrunner / linux-job (gh)
  >>> Lint for extension/vision/test/test_image_processing.py:
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t c0c2f6b9a22e1aaa5077f5bcf173cb985e67fabc5ea59ad4e77d0edcdab0af6e /exec failed with exit code 1
• pull / test-samsung-quantmodels-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 9cee494b91f798d5fa5fd46737f767808d43cfdd7a3b27274596109419eb3c90 /exec failed with exit code 1
• pull / unittest / linux / linux-job (gh)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_8a4w_recipe
• pull / unittest-editable / linux / linux-job (gh)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_8a4w_recipe

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)
  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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[meta-codesync]

@metascroy has exported this pull request. If you are a Meta employee, you can view the originating Diff in D92471879.

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