Close scheduler on module exit

[coolreader18]

Description of Changes

Fixes #2474. Turns out we weren't ever calling Module::close(), and thus were never calling Scheduler::close(). I'm still not able to actually repro the issue but if anything is the cause, this would be it. I also made it so exit().await won't return until the scheduler is fully closed, so that we won't run into race conditions.

Expected complexity level and risk

1

Testing

• [ ] If anyone able to repro the issue would be willing to test (or tell me how to repro) that would be super helpful