[Cherry-pick for 0.20] Expose transforms.v2 utils for writing custom transforms

[NicolasHug]

Cherry-pick of #8670

cc @vfdev-5

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/vision/8673

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 5 New Failures, 1 Unrelated Failure

As of commit d163c95 with merge base db5f8a0 ():

NEW FAILURES - The following jobs have failed:

• CMake / macos (macos-m1-stable) / macos-job (gh)
  CondaValueError: You have chosen a non-default solver backend (libmamba) but it was not recognized. Choose one of: classic
• Lint / c-source / linux-job (gh)
  RuntimeError: Command docker exec -t 6683d42d37fb673f27e8e0924805b2bea450e9f80ba11dd2c610b266ff313ab8 /exec failed with exit code 1
• Tests / unittests-macos (3.10, macos-m1-stable) / macos-job (gh)
  CondaValueError: You have chosen a non-default solver backend (libmamba) but it was not recognized. Choose one of: classic
• Tests / unittests-macos (3.12, macos-m1-stable) / macos-job (gh)
  CondaValueError: You have chosen a non-default solver backend (libmamba) but it was not recognized. Choose one of: classic
• Tests / unittests-macos (3.9, macos-m1-stable) / macos-job (gh)
  CondaValueError: You have chosen a non-default solver backend (libmamba) but it was not recognized. Choose one of: classic

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

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

• Tests / unittests-windows (3.9, windows.g5.4xlarge.nvidia.gpu, cuda, 11.8) / windows-job (gh) (trunk failure)
  AttributeError: '_OpNamespace' 'image' object has no attribute '_jpeg_version'

This comment was automatically generated by Dr. CI and updates every 15 minutes.