Update the ArrayObserver to better account for sort and reverse

[janechu]

Pull Request

📖 Description

This change updates the ArrayObserver to use some array tracking when applying sort or reverse. This will retain state to overcome the problem seen in #6919. No updates are required by developers.

🎫 Issues

Closes #6919

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

[marchbox]

This generally LGTM. My only comment is there are several (array as any), I wonder if it makes sense to type it since it's also different from the argument type array: any[].

[janechu]

This generally LGTM. My only comment is there are several (array as any), I wonder if it makes sense to type it since it's also different from the argument type array: any[].

We are typing it as any in other areas of this file because we are attaching things to the array outside of the normal Array typing, I agree it isn't great... let's extend the typed interface as a separate issue.

[chrisdholt]

🎉