refactor: use listen and trigger universally

- additionally, remove every `unwrap()` call that
could panic, replacing with error propagation
and/or context with `expect()`

- return Result<(), SimulationError> for all
spawned tasks

- handles triggering shutdown at call site for
spawned tasks

- move starting/stopping logs to spawn site

Author: enigbe

.gitignore

@@ -3,4 +3,4 @@ node_modules
 *.json
 activity-generator/releases/*
 .DS_Store
-/results
+/results