fix(engine): Prevent duplicate context creation in React

[felixpalmer]

Implemented against 9.2-release

Background

Using luma in an React environment with StrictMode causes the getMaxDrawingBufferSize() method in canvas-context to be called twice, once with and invalid device, leading to a error (repeated whenever the DOM node is remounted):

Uncaught TypeError: Cannot read properties of undefined (reading 'maxTextureDimension2D')
    at WebGLCanvasContext.getMaxDrawingBufferSize (canvas-context.ts:241:52)
    at WebGLCanvasContext._handleResize (canvas-context.ts:379:62)
    at ResizeObserver.<anonymous> (canvas-context.ts:171:65)
getMaxDrawingBufferSize @ canvas-context.ts:241
_handleResize @ canvas-context.ts:379
(anonymous) @ canvas-context.ts:171

Change List

• Add this.canvasContext.destroy() in webgl-device.ts to cleanup orphaned canvas
• Disconnect observers to prevent callbacks from firing after destruction
• Defensive checks in canvas-context.ts
• Add new hello-react tutorial app to repro bug and help test React integration in future