flow: process evicted flows on low/no traffic

flow: process evicted flows on low/no traffic

In a scenario where there was suddenly no more traffic flowing, flows
in a threads `flow_queue` would not be processed. The easiest way to
see this would be in a traffic replay scenario. After the replay is done
no more packets come in and these evicted flows got stuck.

In workers mode, the capture part handles timeout this was updated to
take the `ThreadVars::flow_queue` into account.

The autofp mode the logic that puts a flow into a threads `flow_queue`
would already wake a thread up, but the `flow_queue` was then ignored.
This has been updated to take the `flow_queue` into account.

In both cases a "capture timeout" packet is pushed through the pipeline
to "flush" the queues.

Bug: #4722.