* Use the declared type to infer NullableContextOptions
Prior to this change MVC used the runtime type rather than the declared type to
determine the nullability of a property based on state. In the case of inheritance,
this can be erroneous since the declared type may have a different nullability context
than the model type.
This change addresses this by adding content to `ModelIdentity` that allows inspecting the
declared type.
* Add an overload to `ModelMetadataIdentity` that allows flowing `PropertyInfo`
* Use the declared type in `DataAnnotationsMetadataProvider` to determine nullability based on context.
Fixes https://github.com/aspnet/AspNetCore/issues/14812
cdae83efae