Timer Timeout Missing Key Context

[Max-Meldrum]

When handling timeouts, we need to also get back the key used so that we can set up the OperatorContext properly. Things may go very wrong now if timers or state calls are used within handle_timeout.

 fn handle_timeout(
    &mut self,
    timeout: Self::TimerState,
    ctx: &mut OperatorContext<Self::TimerState, Self::OperatorState>,
 ) -> ArconResult<Option<Self::ElementIterator>>;