reporter stream buffer is not emptied in all cases

[vigneshshanmugam]

The issue was brought up when users were not seeing heartbeat/summary documents for some of the pages that has more than 200 network requests.

Example test is

step('load homepage', async () => {
  await page.goto('https://www.elastic.co');
});

When the agent is invoked from HB, the agent writes all the events in JSON format and sends journey/end event which is responsible for creating summary event in Heartbeat.

But in some cases we were not seeing the journey/end event and the node process is completed before draining all the items in the stream buffer.

[vigneshshanmugam]

Seems like this issue still exists and can be reproduced for some pages. Opening it to find the root cause.