Introduce initial VHACD based llconvexdecomposition library

[RyeMutt]

Description

This introduces a V-HACD based llconvexdecomposition implementation.

Related Issues

Issue Link: #4475

---

Checklist

Please ensure the following before requesting review:

• I have provided a clear title and detailed description for this pull request.
• If useful, I have included media such as screenshots and video to show off my changes.
• The PR is linked to a relevant issue with sufficient context.
• I have tested the changes locally and verified they work as intended.
• All new and existing tests pass.
• Code follows the project's style guidelines.
• Documentation has been updated if needed.
• Any dependent changes have been merged and published in downstream modules
• I have reviewed the contributing guidelines.

---

Additional Notes

It's currently only enabled in builds where havok is disabled.

Companion autobuild package repository: https://github.com/ryemutt/3p-vhacd

This will require generation of a physicsextensions_stub package without the llconvexdecomposition files.

[Geenz]

LGTM