fix: use array widget when using a OA 3.1 foldable array

[tthornton3-chwy]

Description

When using OA 3.1 and a type like ["array", "null"], the gross json editor was shown, instead of the gorgeous array item picker.

Motivation and Context

This is required because this is a bug.
Fixes: #10943

How Has This Been Tested?

A unit test was added first that recreated the issue, then when we did the code-fixes the test began to pass. We also loaded this into our application using swagger that highlighted the issue, and it properly went away.

Screenshots (if appropriate):

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.