Automatically select credentials in the template credential setup if
there's only one available.
NOTE! This feature is still behind a feature flag. To test, set:
```js
localStorage.setItem('template-credentials-setup', 'true')
```
https://github.com/n8n-io/n8n/assets/10324676/edc1f586-214f-4c37-b7ec-dd1786433dc1