Gizmo updates

[kpal81xd]

Fixes #6981
Fixes #6990

• Gizmo follows nodes when attached
• Updated api to allow gizmo.attach to accept a single node
• Layer is created internally and reused by other gizmos unless specified
• constructor modified to omit app parameter
• Refactored AxisShapes into separate Shape classes
• Added shading flag to TransformGizmo types and set default to false

API changes

• new Gizmo(app: AppBase, camera: CameraComponent, layer: Layer) -> new Gizmo(camera: CameraComponent, layer: Layer)
• gizmo.attach(nodes?: GraphNode[] = []) -> gizmo.attach(nodes?: GraphNode[] | GraphNode = [])
• NEW: const layer = Gizmo.createLayer(app: AppBase, layerName?: string = 'Gizmo', layerIndex?: number | undefined)

N.B The createLayer static function will create a new layer and will add it to the scene. The Gizmo class constructor will append the layer to the camera's set of layers.

Preview

[kpal81xd]

@kungfooman okay found the error mesh instances were trying to be referenced after being destroyed oops