This PR adds ANR detection for Node via a forked child process. The
child process runs the same entry point as the main app. To ensure that
the main app code does not run in the child process, we use a promise
that only resolves in the main process.

When the `captureStackTrace` option is enabled, debugging is enabled in
the main app process and the child process uses WebSockets to capture
stack traces via the v8 inspector API.

Overhead is expected to be minimal. With no ANR detected, the only
overhead in the main app process is polling the child process over IPC
by default every 50ms. The ANR child process consumes around 50-60 MB or
RAM and simply keeps track of the polling. Once ANR has been detected,
the main process will get paused briefly in the debugger to capture a
stack trace frames. At this point, the event loop has been blocked for
seconds so the debugging overhead can be considered negligible.

Once an ANR event has been reported, the child process exits to prevent
further duplicate events.

```ts
import { init, enableANRDetection } from '@sentry/node';

init({ dsn: "__DSN__" });

// ESM supports top-level await
await enableANRDetection({ captureStackTrace: true });
runApp();

// for CJS you'll need then
enableANRDetection({ captureStackTrace: true }).then(() => {
  runApp();
})
```

Co-authored-by: Abhijeet Prasad <devabhiprasad@gmail.com>