Clean up vertex buffer object use (DEFEDIT-1550)

* The {{vertex}} and {{vertex2}} modules are different incompatible implementations of the same thing.
* {{VertexBufferShaderLink}} should not have to store duplicate mesh data on the GPU when only the shader differs.
* The function name {{vtx/use-with}} is curious.

Locate the vertex and vertex2 modules, VertexBufferShaderLink, and vtx/use-with. Compare the two implementations and trace how mesh data is stored and shared when shaders differ. The work is done when the incompatible duplication is resolved and the function naming concern has a clear, consistent outcome.

Written by the indexing model from the issue text.