option for silencing logging for heartbeats

[jlvallelonga]

In development, and possible other environments, it's sometimes nice to not see the heartbeat logging. This adds an option to silence the logging for heartbeats. It's very similar to the "silence_polling" option.

Usage:

  config.solid_queue.silence_heartbeats = true

[rosa]

Thanks @jlvallelonga! However, I was hoping we could get #210 done instead of having a bunch of different options to silence different parts 😅

[jlvallelonga]

Yeah I was thinking about that a bit when I was doing this. Makes sense :)