Unable to determine when all events have been uploaded

[n8ta-msft]

Steps to reproduce. UploadNow() is a non-blocking function

LogManager.UploadNow();
ExitApp();

Will reliably lose telemetry.

For our use case we need to be able to attempt to send telemetry ASAP and have way to know if it has finished before we exit our app. We want to send data right away not flush to disk since this is part of a crash reporter and we do not want to have a long delay before we receive crash information.

Solutions Open to suggestions but we need a way to determine that all, or just a given event, has been sent so we know we can exit. Obviously in some cases it won't be possible to send events so perhaps a callback or a Result return value is needed.