Scene.cpp and Geometry.cpp are large file it can be broken up into smaller easier to handle files. This change has been broken out from #105403 to make understanding the changes easier.
geometry.cpp is broken up into:
1. geometry.cpp
2. geometry_attributes.cpp
3. geometry_bvh.cpp
4. geometry_mesh.cpp
scene.h & scene.cpp is broken into:
1. scene.h
2. scene.cpp
3. devicescene.h
4. devicescene.cpp
Pull Request: https://projects.blender.org/blender/blender/pulls/107079
