SchemaTypeOptions.type is optional

[moander]

type must be optional to support schemas using the typeKey option and nested paths.

This PR reverts a change that was merged a few days ago:
968bd8a#diff-7aa4473ede4abd9ec099e87fec67fd57afafaf39e05d493ab4533acc38547eb8R1367

[vkarpov15]

Unfortunately this change prevents us from throwing an error if the type is incorrect. We'll investigate this further, I'd like to avoid merging this PR as is because of #9857, but we'll see if we can get the best of both.

[vkarpov15]

I took a closer look and the issue comes down to the fact that the value String is a valid SchemaTypeOptions because SchemaTypeOptions has no required keys. That leaves us in a tough spot with supporting checking incorrect schema definitions where the interface has a path set to number but the Schema has that path set to String while still supporting typeKey, because typeKey isn't necessarily known at compile time. The approach on a485c40 will handle the case where the user uses { type: String } rather than just String, that's the best we can do for now 👍