Replace Bullet with Bepu Physics

This project introduces Bepu Physics as an alternative physics engine for Stride 3D, the open-source C# game engine. While we will maintain support for the current Bullet Physics engine, our primary focus will shift towards integrating and optimizing for Bepu.

Why Transition to Bepu Physics?
Bepu Physics offers a range of compelling advantages over Bullet, making it the ideal choice for Stride 3D's evolving needs:

Performance
Bepu Optimized for C# and designed with modern hardware in mind, Bepu delivers superior performance and scalability. It excels in multi-threaded scenarios, allowing complex simulations to run efficiently. Since Stride 3d is C# based, using a fully C# build physics engine simply ties in better with our ecosystem.

Ecosystem Integration
Bepu built natively for .NET, Bepu integrates seamlessly with Stride's C# environment, reducing complexity and eliminating the need for interop layers.

Flexibility
Bepu provides a highly modular and customizable framework, allowing developers to tailor simulations to their specific needs with minimal effort.

Future-Proofing
Bepu actively maintained and designed to leverage modern development practices, ensuring long-term viability.

https://opencollective.com/stride3d/projects/bepu-physics

The issue proposes adding Bepu Physics as an alternative and shifting primary focus away from Bullet Physics in Stride 3D. No files, tests, or entry points are identified, so start by locating the existing Bullet integration and evaluating the engine architecture and compatibility requirements. Done would require a defined integration plan and working Bepu support, but the issue does not specify acceptance criteria.