core: darwin: Input callbacks, corrected framebuffer/window sizes, swapchain handling

[foxnne]

Requires this mach-objc PR to be merged before we can update the zon for this one.

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[foxnne]

Recent changes allow pinch to zoom and a new event to handle that. I also have picked up the change to window.color and created the desired fields, decorated, transparent and decoration_color.

[foxnne]

Currently remaining basic missing features Pixi wants:

• Cursor control
• Character input