Fix ApiExplorer metadata for FormFiles/Stream/PipeReader in MVC actions

[captainsafia]

MVC uses the FormFileModelBinder (ref) to support binding for IFormFile, IFormFileCollection, and IEnumerable<FormFile>.

When this is the case, the ApiExplorer layer will produce 6 distinct parameter descriptions for each property within the IFormFile type:

This is distinct from the descriptions that are generated for minimal APIs which correctly produces the correct binding sources for form file parameters (see https://github.com/dotnet/aspnetcore/blob/main/src/Mvc/Mvc.ApiExplorer/src/EndpointMetadataApiDescriptionProvider.cs#L305). We should update the MVC implementation of ApiExplorer to do the right thing.

[captainsafia]

This issue also occurs with Stream and PipeReader inputs in MVC which are handled by the BodyModelBinder and end up being splatted out into the public properties on each respective type.

[mkArtakMSFT]

Removing the milestone to retriage.