[collision] Add vertex collisions to octree collision detection

[IAmNotHanni]

Not ready for review yet

• Refactor the rendergraph so that every octree has its own vertex and index buffer and its own uniform buffer

Closes #406

TODO

• Iterate through octree worlds in order of increasing distance to camera
• Store center of a cube instead of calculating it every time
• Find a solution for taking grid size into account
• Render the vertex which collides with the camera ray in a different color
• Improve reference page about octree collision detection #388

Tests and Benchmarks

• Add new automated tests (inexor-vulkan-renderer-tests)
• Add new automated benchmarks (inexor-vulkan-renderer-benchmarks)

Outlook

• Implement a simple octree editor #234
• Implement missing Cube methods #190
• How to make handles to cube class both thread safe and efficient? #419

[IAmNotHanni]

So I have been thinking about it and it really makes sense to refactor the rendergraph a little first so that every octree has its own vertex and index buffer and its own uniform buffer before I merge this.