Agent doesn't capture uncaught exceptions or unhandled rejections

**Describe the bug**

Suddenly my Express applications do not capture errors or exceptions that cause the application to crash. Up until the 21st of February I can see both in the Error tab of the APM and in the Discover tool of ELK that there were crashes reported due to silly mistakes, like a missing environment variable. But nothing since then. And I've tried to crash the application deliberately adding `throw new Error('Boom')` and `Promise.reject(new Error('Kaboom'))` and neither is reported by the APM.

Investigating any possible changes I've made I can only think of upgrading the agent's version from 3.42.0 to 4.3.0. But I've tried with the old version and it behaves the same way.

**To Reproduce**

package.json

```
{
"type": "module",
"name": "experiment",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC",
"dependencies": {
"elastic-apm-node": "^4.5.0",
"express": "^4.19.2"
}
}
```

index.js

```
import './apm.js'; // Must go first
import express from 'express';

const port = 3000;
const app = express();

app.get('/', (_req, res) => {
//Promise.reject(new Error('Kaboom')); // Uncomment either of these
res.send('Hello World!');
});

app.listen(port, () => {
console.log(`Example app listening on port ${port}`);
});

//throw new Error('Boom'); // Uncomment either of these
```

apm.js

```
import apm from 'elastic-apm-node';

apm.start({
environment: 'local',
serverUrl: 'https://example.com:12345/',
});
```

**Expected behavior**

Uncaught exceptions and unhandled rejections being reported by the agent so that they can be monitored in the APM tool of ELK.

**Environment (please complete the following information)**

- OS: Linux and MacOS
- Node.js version: 16.16.0
- APM Server version: 7.17.8
- Agent version: 3.42.0 and 4.3.0

**How are you starting the agent? (please tick one of the boxes)**

- [x] Calling `agent.start()` directly (e.g. `require('elastic-apm-node').start(...)`)
In particular, I have a `init-elastic-apm.ts` file where I start the agent with a config dependent on some environment variables. Then the first line of my `index.ts` file is `import apm from 'elastic-apm-node'`.
- [ ] Requiring `elastic-apm-node/start` from within the source code
- [ ] Starting node with `-r elastic-apm-node/start`

**Additional context**

Agent config options:

Click to expand

```
import { hostname } from 'node:os';
import pkg from '../../package.json' assert { type: 'json' };
{
serviceName: pkg.name.split('/')[1],
serviceVersion: pkg.version,
serviceNodeName: hostname(),
environment: process.env['APP_ENV'],
serverUrl: process.env['ELK_KIBANA_URL'],
captureBody: 'all',
captureExceptions: true, // <-- I've tried with default and explicit `captureExceptions`
}
```

`package.json` dependencies:

Click to expand

```
"@aws-sdk/client-s3": "3.245.0",
"@aws-sdk/client-timestream-write": "3.245.0",
"@bluesialia/express-graphql": "0.15.0",
"@elastic/ecs-pino-format": "1.5.0",
"@sentry/node": "7.103.0",
"bcryptjs": "2.4.3",
"body-parser": "1.20.1",
"compression": "1.7.4",
"cors": "2.8.5",
"dotenv": "16.3.1",
"elastic-apm-node": "3.42.0",
"express": "4.18.2",
"express-async-errors": "3.1.1",
"extract-files": "13.0.0",
"firebase-admin": "11.10.1",
"google-auth-library": "8.7.0",
"graphql": "16.6.0",
"graphql-scalars": "1.20.1",
"graphql-upload": "13.0.0",
"graphql-ws": "5.11.2",
"http-status": "1.6.1",
"jszip": "3.10.1",
"knex": "2.4.0",
"modern-async": "1.1.3",
"node-fetch": "3.3.2",
"objection": "3.1.4",
"objection-paginator": "0.7.1",
"paddle-sdk": "3.2.0",
"pg": "8.8.0",
"pino": "8.17.1",
"stringify-object": "5.0.0",
"wasmagic": "0.0.32"
```