Consider returning a promise from flush method in node tracker

Is your feature request related to a problem? Please describe.
Currently gotEmitter's flush method is not async and returns void instead of a promise.
This makes it harder to use in environments where a promise is needed to ensure all async tasks complete before exiting (e.g. AWS Lambda async handlers).

Describe the solution you'd like
flush is async/returns a promise.

Describe alternatives you've considered
At the moment the way to ensure flush completes in such environments is to wrap the emitter in a promise, and configure it with a callback that resolves and rejects that promise.

Start by locating the gotEmitter flush implementation and its existing callback path. Trace how asynchronous tasks signal completion, then verify that flush resolves or rejects only after those tasks finish and that existing callback behavior remains covered by the relevant tests.