WIP : ofAppGLFW improvements

[dimitre]

changes:

• callback stored for new monitors connected / disconnected / changed resolution or even position, so the data is cached.
• fix this issue https://github.com/openframeworks/openFrameworks/issues/6895
• getWindowRectangle / setWindowRectangle to simplify operations
• fixed issue that an app started with OF_FULLSCREEN cannot recover the proper dimensions
• when entering fullscreen it is considering window getCenter in relation to the monitors
• macOS: fullscreen has no shadow so it doesn't bleed to other window. shadow is back when windowed. Most of the changes were made macOS only
• now setWindowRectangle uses GLFW glfwSetWindowMonitor which can set position and dimensions at the same time to ensure consistency on macOS
• window dimensions now stopped using pixelScreenCoordScale
• "settings.monitor not being clamped" issue fixed. this functionality is now outside GAME_MODE, FULLSCREEN and WINDOW ifs, so it happens only once.
• added windowRefreshCallback so the framebuffer doesn't blink streched when toggling fullscreen. this can be investigated with a very low framerate. related:
• https://github.com/openframeworks/openFrameworks/issues/6953
• https://github.com/openframeworks/openFrameworks/issues/6950