perf: container sorting

packages/graphics/src/container.js

@@ -240,9 +240,22 @@ export default class Container extends Renderable {
         child.sort();
       }
     }
-    this.$$children.sort((l, r) => l.$$zIndex - r.$$zIndex);
+    // Double insertion sort, because mostly-sorted is the usual case.
+    for (let i = 1; i < this.$$children.length; i++) {
+      const current = this.$$children[i];
+      const currentChild = this.container.isFake ? undefined : this.container.children[i];
+      let j = i - 1;
+      while ((j > -1) && (current.$$zIndex < this.$$children[j].$$zIndex)) {
+        this.$$children[j + 1] = this.$$children[j];
         if (!this.container.isFake) {
-      this.container.children = this.$$children.map((child) => child.internal);
+          this.container.swapChildren(this.container.children[j], this.container.children[j + 1]);
+        }
+        j--;
+      }
+      this.$$children[j + 1] = current;
+      if (!this.container.isFake) {
+        this.container.swapChildren(currentChild, this.container.children[j + 1]);
+      }
     }
   }