Sort using more deterministic algorithm

`hypot` while useful for most of the cases, may break sorting
assumptions like deterministic comparison.
As seen in: https://github.com/pop-os/cosmic-launcher/issues/352

Add and use a new method that trades the performance for more
determinism.

graphics/src/damage.rs

@@ -49,8 +49,8 @@ pub fn group(mut damage: Vec<Rectangle>, bounds: Rectangle) -> Vec<Rectangle> {
 
     damage.sort_by(|a, b| {
         a.center()
-            .distance(Point::ORIGIN)
-            .total_cmp(&b.center().distance(Point::ORIGIN))
+            .distance_slow(Point::ORIGIN)
+            .total_cmp(&b.center().distance_slow(Point::ORIGIN))
     });
 
     let mut output = Vec::new();