Refactor: Rename getLogicalSize → getCanvasSize for better clarity

[halx99]

"CanvasSize" better reflects the logical 2D space used for scene layout and initialization. Improves readability and avoids confusion with device resolution or safe area concepts.

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Axmol 3.x ------------------------------------------------------------

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TODO:

mark: getFrameSize, setFrameSize, getWinSize, setFrameZoomFactor, getFrameZoomFactor in axmol-2.9.0

[halx99]

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