Fix #3504: Don't use time module in pew.tick()

[deshipu]

The time.sleep() and time.monotonic() functions break the timer
interrupt on which PewPew10 display relies, so we can't use them
anymore. Instead I'm adding a time-keeping function to the display
code itself, which then can be used in pew.tick() internally.

[deshipu]

This is a proof of concept for the fix. If we agree to it, I will also need to add a corresponding code change to the frozen pew.py library to make use of this function.

[tannewt]

I replied on the issue. I suspect we won't need this.

[deshipu]

Fixed by #3546

[deshipu]

I would like to reopen this pull request. If I avoid relying on the time.monotonic() entirely, there is zero flicker in PewPew, and I don't run into problems with lowering accuracy over time.

[dhalbert]

This is OK by me, since it doesn't change anything else except your own library.

[dhalbert]

If we had some kind of ticks_ms() routine that wrapped around for non-longints, would that be useful to you instead?

[deshipu]

No, an important feature here is that it doesn't use the timekeeping/sleep machinery, and so doesn't trigger the flickering.

[tannewt]

I don't think it's the timekeeping/sleep machinery causing you problems. All of those things are still happening. I'd blame monotonic's degrading accuracy if anything.

[deshipu]

In any case, this solves the problem and makes it unlikely to ever come back, which is important for me from the maintenance point of view.