salad: performance and reliability fixes

Well, turns out checking the list of serial adapters thousands of times per seconds may not be the most efficient thing to do :D

To fix this, we simply split the "update_ports" function into to:

• removing consoles that are broken (run every loop)
• adding new serial consoles (run every second)

With these changes, my computer can handle millions of lines per second. I'll add my profiling script as part of the MR tomorrow :)