This is a speculative fix to leftover tmp directories.
When users issues SIGINT twice, we enter `gracefullyClose()`
twice, and shortcut the second time. It turns out, we do
not wait for directories removal.
Note: it is unknown how often we reach this codepath in practice.
This changes PlaywrigtServer to serve connections like `ws://localhost:3333/?browser=chromium`:
- launches the browser;
- talks `browserType.connect`-style protocol over websocket;
- compatible with `connectOptions` fixture.
```js
await playwright.chromium.connect({ wsEndpoint: 'ws://localhost:3333/?browser=chrome' });
```
