fix(v1): handle `_key` and `_type` in objects

[ochicf]

Fixes https://github.com/ricokahler/sanity-codegen/issues/236

The strategy taken has been to recursively forward an ancestors array so the parent is available when generating the types for a node. Ff current node is object and parent is array, then it add _key and _type.

Let me know if those fields should be added in any other cases.

Also @ricokahler I'm not able to run tests, so I have not updated them. But I think it would be good to add a case to ensure this is kept on future refactors/changes.