Overlays do not extend to the edges of the canvas

[MrStevns]

Issue Summary

Currently the overlays uses a fixed length factor which means that they become unusable as guides when zooming too far out.

Actual Results

The lines are drawn with a fixed length factor

Expected Results

The lines always extend to the region of the canvas, no matter the zoom level.

Video or Image Reference

Steps to reproduce

1. Enable any perspective tool
2. Zoom out

System Information

• Pencil2D Version: master: 855c42307213fc67f7ea805eb30432f5c42b1276