SVGRenderer: Add depth sorting for Sprites and SVGObjects

[mrdoob]

Description

Implements z-depth sorting between geometric elements (faces, lines), Sprites, and custom SVGObjects in SVGRenderer.

Changes:

• Added unified render list that merges and sorts all renderable items (elements, sprites, and SVGObjects) by render order and z-depth
• Implemented GC-free stable sort for both Projector and SVGRenderer to avoid garbage collection during rendering
• Optimized object pooling pattern for zero-allocation rendering
• Added OrbitControls to svg_sandbox example for interactive testing

Screen.Recording.2025-11-07.at.6.02.03.PM.mov