Code review comment for lp://qastaging/~afrantzis/mir/buffer-bind-to-render-image

There's a whole bunch of Mir code that talks about Buffers but is not either the BufferAllocator or the Renderer - BufferQueue, BufferBundle, Compositor, the frontend all have some interaction with Buffers; none of these care about the buffer content. Triplicating all of these - GL, Vulkan, blit - seems a bit excessive.

We *could* plausibly provide these as templates that the platform specialises, but that's a significant undertaking.

Hm. That might end up being a much better fit, actually. As I've mentioned before, I'm not sure that an EGLStream-based platform would fit our current abstractions.