Add Path type annotation for ImageFolder

[NicolasHug]

Closes #8525

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/vision/8526

• 📄 Preview Python docs built from this PR

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

❌ 2 New Failures, 4 Unrelated Failures

As of commit 46a64d9 with merge base 87d05c6 ():

NEW FAILURES - The following jobs have failed:

• Tests / unittests-windows (3.8, windows.4xlarge, cpu) / windows-job (gh)
  The process 'C:\Program Files\Git\cmd\git.exe' failed with exit code 128
• Tests / unittests-windows (3.9, windows.4xlarge, cpu) / windows-job (gh)
  The process 'C:\Program Files\Git\cmd\git.exe' failed with exit code 128

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• Tests / unittests-macos (3.11, macos-m1-stable) / macos-job (gh) (detected as infra flaky with no log or failing log classifier)

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

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

• Tests / unittests-windows (3.10, windows.4xlarge, cpu) / windows-job (gh) (trunk failure)
  Process completed with exit code 2.
• Tests / unittests-windows (3.11, windows.4xlarge, cpu) / windows-job (gh) (trunk failure)
  Process completed with exit code 2.
• Tests / unittests-windows (3.12, windows.4xlarge, cpu) / windows-job (gh) (trunk failure)
  Process completed with exit code 2.

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