[Data masking] Provide solution for TypeScript type compatibility for APIs that use both the masked result and full result

[jerelmiller]

With the introduction of data masking throughout Apollo Client, there are some APIs that use both the masked result and the full result. For example, useMutation returns a data property that is masked, but the update callback receives the full unmasked result. This creates a problem with the existing typings since right now you can only specify one or the other. We'll need to create something that can handle both.