Chore: Separate language examples into intuitive tabs

https://redot-docs-site.pages.dev/docs/Classes/AStar3D


<img width="984" height="763" alt="Image" src="https://github.com/user-attachments/assets/20585aff-8601-480a-b351-c47bbd098cdd" />

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https://redot-docs-site.pages.dev/docs/Classes/AStarGrid2D

<img width="984" height="674" alt="Image" src="https://github.com/user-attachments/assets/70d13e4c-9457-478b-9724-0faef145a755" />