Improve our React test suite

[joshblack]

Currently, our test suite is a mix of enzyme, React Testing Library, and a custom solution with an RTL-like API. This epic tracks our refactor efforts for our React test suite which should include the following updates:

Tasks

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1. An official "testing style guide" that maintainers and contributors can reference when authoring or updating components
2. React 18 Migration: Refactor the React test suite to use React Testing Library #10184
   131 of 131
   epic planning: umbrella +2
3. An exploration into e2e visual testing tools like Cypress or playwright to see how easily we could author tests in these environments and how effective they would be
4. test(project): add e2e test support with playwright #11302
   +0
5. Complete accessibility-checker baseline for React components #9475
   planning: umbrella +1
   
6. Increase a11y-checker coverage, test component states (focus, hover, open/close, etc.) #11370
   planning: umbrella +1
7. Add the eslint-plugin-testing-librarypackage to our eslint config #9048
   role: dev 🤖 type: infrastructure 🤖 +2
8. Add the eslint-plugin-jest-dom package to our eslint config #13312
   0 of 3
   role: dev 🤖 +1