use perf_hooks

Summary:
We were using `window.performance` to measure performance. This was because the equivalent node.js API `perf_hooks` wasn't available in the electron version we were using back then.
However, `perf_hooks` has landed in electron meanwhile, so I am moving to this API, as it works for the headless version and jest tests, too.

This allows us to delete the babel transform that was used for node-based tests, where the browser API was replaced with the node API

Reviewed By: jknoxville

Differential Revision: D13860133

fbshipit-source-id: cf1395004fac046dd55751ff465af494173b2cbf

src/plugins/layout/index.js

@@ -27,6 +27,8 @@ import {
   ToggleButton,
   SidebarExtensions,
 } from 'flipper';
+// $FlowFixMe perf_hooks is a new API in node
+import {performance} from 'perf_hooks';
 
 import type {TrackType} from '../../fb-stubs/Logger.js';