add test for dispatcher kernel signature consistency

[pmeier]

This test makes sure the dispatchers and the kernels have the "same" signature within the rules we defined for exceptions. Meaning,

1. The kernels are allowed to require extra metadata that is only passed explicitly to the dispatcher through the feature, e.g.

   vision/torchvision/prototype/transforms/functional/_geometry.py

   Line 51 in cb4413a

   def horizontal_flip(inpt: features.InputTypeJIT) -> features.InputTypeJIT:

   vision/torchvision/prototype/transforms/functional/_geometry.py

   Lines 30 to 32 in cb4413a

   	def horizontal_flip_bounding_box(
   	bounding_box: torch.Tensor, format: features.BoundingBoxFormat, spatial_size: Tuple[int, int]
   	) -> torch.Tensor:

2. The kernels are allowed to "drop" some parameters if they are nonsensical for the feature type in question, e.g.

   vision/torchvision/prototype/transforms/functional/_geometry.py

   Lines 203 to 209 in cb4413a

   	def resize(
   	inpt: features.InputTypeJIT,
   	size: List[int],
   	interpolation: InterpolationMode = InterpolationMode.BILINEAR,
   	max_size: Optional[int] = None,
   	antialias: Optional[bool] = None,
   	) -> features.InputTypeJIT:

   vision/torchvision/prototype/transforms/functional/_geometry.py

   Line 164 in cb4413a

   def resize_mask(mask: torch.Tensor, size: List[int], max_size: Optional[int] = None) -> torch.Tensor:

Currently there are two failures:

_____________ TestDispatchers.test_dispatcher_kernel_signatures_consistency[resize-Image] _____________
Traceback (most recent call last):
  File "/home/user/vision/test/test_prototype_transforms_functional.py", line 351, in test_dispatcher_kernel_signatures_consistency
    assert dispatcher_param == kernel_param
AssertionError: assert <Parameter "antialias: Union[bool, NoneType] = None"> == <Parameter "antialias: bool = False">
__________ TestDispatchers.test_dispatcher_kernel_signatures_consistency[resized_crop-Image] __________
Traceback (most recent call last):
  File "/home/user/vision/test/test_prototype_transforms_functional.py", line 351, in test_dispatcher_kernel_signatures_consistency
    assert dispatcher_param == kernel_param
AssertionError: assert <Parameter "antialias: Union[bool, NoneType] = None"> == <Parameter "antialias: bool = False">

I don't know if they are deliberate or not.

cc @vfdev-5 @datumbox @bjuncek

[pmeier]

If you like me are wondering why the video kernels are not showing up, although they have the same issue as the image kernels above: we simply forgot to "tell" our tests that the dispatchers now also handle videos. See #6905 for a fix.

[datumbox]

@pmeier Thanks for the fix. Will this handle cases where we have declared things optional like in #6902?

[datumbox]

LGTM, thanks!