Adds 1 minute delay on record for [exporter-stackdriver]

[isaikevych]

No description provided.

[songy23]

One high-level comment: I think a better way may be:

1. For every onRecord, still generate timeSeries synchronously.
2. Buffer the timeSeries in an array and export them to backend every 1 minute (or other configured delay) asynchronously.
3. Export should go in parallel with onRecord, i.e shouldn't block each other.

This is what we did in other languages. What do you think?

[isaikevych]

One high-level comment: I think a better way may be:

1. For every onRecord, still generate timeSeries synchronously.
2. Buffer the timeSeries in an array and export them to backend every 1 minute (or other configured delay) asynchronously.
3. Export should go in parallel with onRecord, i.e shouldn't block each other.

This is what we did in other languages. What do you think?

I need to invest some time for refactoring, because current implementation uses language specific approach. Also, I am using Promise for this needs, which is readable for nodejs devs.

[songy23]

Discussed offline, since the timeout is async (a common practice in Node) and won't block the onRecord, we can go ahead and merge this change for now. We'll investigate how to refactor this code in another issue.

[isaikevych]

TODO: #152