Roll out new egui icon and logo (#7995)

For the first time _ever_, egui has a logo!

<img width="3925" height="1406" alt="egui-logo"
src="https://github.com/user-attachments/assets/cfaf1d43-9338-490f-ae82-99b420baa1b0"
/>

Made by [Studio Gruhl](https://www.studiogruhl.com/) and paid for by
[Rerun.io](https://rerun.io/).

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