Refactor away lifecycle hooks deprecated in React 17

The following components throw lint errors because they use the deprecated React lifecycle hook, componentWillUpdate.

componentWillUpdate is deprecated since React 16.3.0, use UNSAFE_componentWillUpdate instead, see https://reactjs.org/docs/react-component.html#unsafe_componentwillupdate

lib/ProxyManager/ProxyManager.js
lib/SearchAndSort/SearchAndSort.js

✖ 2 problems (2 errors, 0 warnings)

To not use the UNSAFE method, we need to use getDerivedStateFromProps or componentDidUpdate. The former occurs before render, but is a static method, meaning it cannot access `this` (instance props). The latter occurs after render() and cannot update the state (which would cause flickering); it is often used to apply focus() to an element.