fix(core): destroy CanvasContext on finalize to prevent memory leak

[LeLunZ]

Closes #10355

Background

When unmounting a Deck instance (both standalone and via wrappers like MapboxOverlay), a memory leak occurs where detached DOM nodes (the <canvas>) and Deck instances are never garbage collected.

Previously, Deck.finalize() simply dropped the reference to this._canvasContext. Because this._canvasContext?.destroy() was never explicitly called, luma.gl's Surface superclass never ran _stopObservers(). As a result, the ResizeObserver and matchMedia listeners remained permanently bound to the Window, creating a strong GC root that kept the detached canvas and Deck instance alive indefinitely.

Note: This was originally observed using MapboxOverlay.

Change List

• destroy CanvasContext on finalize to prevent memory leak