Prerender

Changed
- Removed the `Page.addScriptToEvaluateOnNewDocument({source: 'localStorage.clear()'})` since it seemed to be causing an issue with Chrome in some cases. Going to look for a better fix here since our context should be clearing this already.

Changed
- For checking if a URL returns a redirect, we were checking to see if the request returning the redirect URL matched which failed in some cases where the encoding of the URL was different in the request. That code now checks the request ID to see if it matches the original request.
- Service worker enable/disable can be enabled/disabled on a per tab basis by setting `req.prerender.enableServiceWorker` in the `requestReceived` event.

Changed
- Added ability to turn on/off services workers.

Added
- Added `this.isBrowserConnected = false` inside `server.restartBrowser()` so the prerender server won't try to render any new requests before the browser is actually restarted. Fixes a very small edge case at scale.

Added
- Added `localStorage.clear()` on a new page being loaded due to bug in BrowserContext local storage being cleared: https://bugs.chromium.org/p/chromium/issues/detail?id=754576

Changed
- Changed `document.getElementsByTagName('html')[0].outerHTML` to `document.firstElementChild.outerHTML` when querying page `html` to improve performance.

Changed
- Make sure we only call `Buffer.byteLength` on a string to fix an error in newer versions of Node