Upgrade Web UI to Create-React-App 4 and React 17 (#1105)

* Upgrade to CRA 4.0.3

* Try to fix tests. No lucky

* Fix new ESLint errors

* Fix JS tests and remove unwanted dependency. (#1106)

* Fix tests

* Fix lint

* Remove React v16 workaround (fixed in v17)

* Force eslint to break on warnings

* Lint now needs to be called explicitly in the pipeline

Co-authored-by: Yash Jipkate <34203227+YashJipkate@users.noreply.github.com>

ui/src/index.js

@@ -4,7 +4,12 @@ import './index.css'
 import App from './App'
 import * as serviceWorker from './serviceWorker'
 
-ReactDOM.render(<App />, document.getElementById('root'))
+ReactDOM.render(
+  <React.StrictMode>
+    <App />
+  </React.StrictMode>,
+  document.getElementById('root')
+)
 
 // If you want your app to work offline and load faster, you can change
 // unregister() to register() below. Note this comes with some pitfalls.