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/Client.js

@@ -14,6 +14,8 @@ import type {OS} from './devices/BaseDevice.js';
 import {FlipperDevicePlugin} from './plugin.js';
 import {setPluginState} from './reducers/pluginStates.js';
 import {ReactiveSocket, PartialResponder} from 'rsocket-core';
+// $FlowFixMe perf_hooks is a new API in node
+import {performance} from 'perf_hooks';
 
 const EventEmitter = (require('events'): any);
 const invariant = require('invariant');