[WIP] Remove parent tile workaround

[jacobtylerwalls]

This branch removes the workarounds for parent tile linking and the last custom serializers.

It works with the core branch I just pushed to support nested tile writes. I'll keep testing with cardinality N early next week(*) (which would just be an array), but this branch allows cardinality 1 like:

"right": {
    "right_statement": {
         "right_statement_content": "foo"
    }
}

Marking this PR as draft until I do that additional testing with cardinality N.

(*) And then honestly I'll be at the point where I can pull this out into an arches app and write some tests to get ready for a round of reviews. 🙏