Resolve deprecation warnings in unit tests

[jtimpe]

Background

#1577 upgraded react-scripts to version 5, along with most other frontend dependencies. After the upgrade, some libraries used in our unit tests are reporting some deprecations.

• wrapper.find

  Warning: findDOMNode is deprecated and will be removed in the next major release. Instead, add a ref directly to the element you want to reference. Learn more about using refs safely here: https://reactjs.org/link/strict-mode-find-node
  

• redux configureStore

  The signature '(middlewares?: Middleware<{}, any, Dispatch<AnyAction>>[] | undefined): MockStoreCreator<any, {}>' of 'configureStore' is deprecated.
  

Acceptance Criteria

• findDOMNode deprecation is resolved
• configureStore deprecation is resolved
• Testing Checklist has been run and all tests pass
• README is updated, if necessary

Tasks

• Investigate best practices for redux configureStore (possibly consider redux-toolkit)
• Replace instances of configureStore with best practice where applicable
• Implement replacement of findDOMNode
• Run Testing Checklist and confirm all tests past