Fix DTD prototype dataset on Windows (#5227)

* [DEBUG] run prototype tests on Windows

* disable duplicate resource class

* fix newlines in mock data generation

* fix path matching for DTD

* revert CI changes

* Revert "fix newlines in mock data generation"

This reverts commit f53cf60ff5638e6c2e08a0ee2e73d646b051395f.

* rerun tests with fix in torchdata

* revert CI changes

* add explanation

torchvision/prototype/datasets/_builtin/dtd.py

@@ -72,7 +72,8 @@ class DTD(Dataset):
 
     def _image_key_fn(self, data: Tuple[str, Any]) -> str:
         path = pathlib.Path(data[0])
-        return str(path.relative_to(path.parents[1]))
+        # The split files contain hardcoded posix paths for the images, e.g. banded/banded_0001.jpg
+        return str(path.relative_to(path.parents[1]).as_posix())
 
     def _collate_and_decode_sample(
         self,