[#3284] perf: reduce allocations for GraphicsGroup draw calls (#3285)

Closes #3284 

## Changes:

- reuse single cumulative bounding box for local bounds calculation of `GraphicsGroup` to reduce per-draw allocations

CHANGELOG.md

@@ -238,6 +238,7 @@ are doing mtv adjustments during precollision.
   * `EventEmitter`s
   * `GraphicsSystem` entity iteration
   * `PointerSystem` entity iteration
+- Perf improvements to `GraphicsGroup` by reducing per draw allocations in bounds calculations
 
 ### Changed
 

src/engine/Graphics/GraphicsGroup.ts

@@ -58,16 +58,16 @@ export class GraphicsGroup extends Graphic implements HasTick {
   }
 
   public get localBounds(): BoundingBox {
-    let bb = new BoundingBox();
+    const bb = new BoundingBox();
     for (const member of this.members) {
       if (member instanceof Graphic) {
-        bb = member.localBounds.combine(bb);
+        member.localBounds.combine(bb, bb);
       } else {
         const { graphic, offset: pos, useBounds } = member;
         const shouldUseBounds = useBounds === undefined ? true : useBounds;
         if (graphic) {
           if (shouldUseBounds) {
-            bb = graphic.localBounds.translate(pos).combine(bb);
+            graphic.localBounds.translate(pos).combine(bb, bb);
           }
         } else {
           this._logger.warnOnce(`Graphics group member has an null or undefined graphic, member definition: ${JSON.stringify(member)}.`);