Send terminated output when canceling a concurrent input.

[danielshaar]

The worker will ignore the terminated outputs for now. We should wait until at least Thursday 4pm ET before releasing this to ensure all workers have rolled out with the ignoring logic.

Context in WRK-11.

[freider]

We don't need to send these messages if only one input is running on a container.
Why not? Concurrency=1-containers also need to escalate if they don't respond gracefully to single input cancellations, and I think it would be nice if the worker can always assume getting a FunctionPutOutputs for each input unless something bad happens

[freider]

We might also want to add some assertions in relevant container_tests (there are plenty for various different cancellation conditions) that FunctionPutOutputs is sent

[freider]

lgtm!