gfx/renderer/private: corrected resource teardown.¹

1: What a dumb mistake!
utility/utility: added ArrayRef and array_ref() for tidier looping of parameterized arrays.
gfx/types: tidy.
gfx/renderer: removed VertexFormat from vertex buffer definition.¹

1: This will become part of a "buffer binding" definition for
geometry that encapsulates a VAO in OpenGL.
gfx/types: added NUM to VertexAttribType.