Add a signal compressor for the canvas offset (rulers update)

Rulers were updated at a very high frequency during canvas transformations (more than 200 times per second). A delay >80 ms is needed for a visibly smoother operation.

Do note however, that this will make the ruler updates visibly choppy! There was already a zoom compressor in place, but it never really worked, because the zoom signal provoked the offset signal, and the update happened anyway at real-time frequency instead of the previous 80 ms.

Unfortunately, in my testing on a 144Hz display, even 80 ms delay is insufficient to get a really smooth canvas panning. 120 ms seemed to work, but I went with 160 ms to be safe as it really doesn't make much difference for the rulers at that point.

TL;DR This patch will make canvas operations visibly smoother, at the cost of slower ruler updates. You can see the ideal performance with the rulers hidden, but the added compressor should get us closer to that ideal.

EDIT Sorry, forgot to mention that this doesn't really help anything (on my system) if my display is set to 60Hz. I'm curious if anyone else sees the benefit in such situation. If not, then I suppose adding this patch (or at least using the delay of 160 ms) may be questionable. Still, I believe even a short compressor should be added to avoid the excessive triggering.