Experimental: Save CPU When Losing Focus

[r888800009]

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TL;DR: Refactor event handling and add performance option

This update saves power without requiring changes to animation and physics animations.

• Refactored the event handling in the incBeginLoop function to use a state machine for managing poll and wait modes, reducing CPU usage when the application is not focused.
• Added a new performance option in the settings window called Render Only When Window Focused. Enabling this option stops rendering when the window loses focus, further reducing CPU usage.
• This feature is enabled by default

Related issue: https://github.com/nijigenerate/nijigenerate/issues/21