Refactor mesh loader part of code and interfaces in base class.

[zz990099]

Update Summary​​

1. The mesh loader functionality has been abstracted, enabling users to implement custom model loading pipelines.
2. FoundationPose now outputs poses in the ​​mesh coordinate frame​​ (convert to bounding box coordinates using ConvertPoseMesh2BBox from mesh_loader.hpp).
3. Register and Track processes are fully decoupled - no longer maintaining internal pose state between calls.

These changes are available in the develop_refactor_mesh_loader branch.

​​We welcome testing and feedback!​

[godfather1402]

Hi @zz990099 , thank you very much. The pose is correct now :)