Conversion to useExternalStore

[mrclay]

What is the purpose of this pull request? (put an "X" next to item)

[ ] Documentation update [ ] Bug fix [ ] New feature [ ] Other, please explain:

What changes did you make? (Give an overview)

Which issue (if any) does this pull request address?

Is there anything you'd like reviewers to focus on?

Failing lines in onAfterUpdate.test.tsx:

• [ ] 41
• [ ] 89
• [ ] 138
• [ ] 215
• [ ] 484