Provide an async waiting mechanism

[fargito]

Currently the way we check if events have been properly sent is quite basic:

• we trigger the trail matching the required pattern
• we execute some code to get the event to be sent
• we wait an arbitrary amount of time
• we retrieve the events from the trail
• we assert with the content of the trail

This works, but is suboptimal, since increasing the wait time can lead to more reliable results, but on the same time increase our overall test duration. On the contrary, reducing the wait time can cause the tests to become flaky.

We should not have to manually wait at all.

The API could look something like:

await eventScoutClient.toContainEvents(
      // some assertions, for example
      expect.arrayContaining([
        expect.objectContaining({
          source,
          'detail-type': detailType,
          // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
          detail: expect.objectContaining({
            toto: 'tata',
            runId,
          }),
        }),
      ])
);