Avoid resetting Websocket idle_timeout timer too often

`perf` has shown that Cowboy spends a lot of time
cancelling and starting this timer. Instead of resetting
for every data received, we now only reset a field in the
state.

Before it was working like this:

- start idle timeout timer
- on trigger, close the connection
- on data, cancel and start again

Now it's working like this:

- start idle timeout timer for a tenth of its duration, with tick number = 0
- on trigger, if tick number != 10
  - start the timer again, again for a tenth of its duration
  - increment tick number
- on trigger, if tick number = 10
  - close the connection
- on data, set tick number to 0

0 files changed, 0 insertions, 0 deletions