Uniform data/buffers

[Try]

Vulkan api on this side is quite messy - need to design nice engine-level api.

Use-cases:

1. Per-frame immediate data (view/proj matrix, main light)
2. Per-draw immediate data (obj matrix)
3. Constant data (vbo/ibo, animation skeleton to some extend)

case 3 is native - DescriptorSet::set
case 2 almost works, as push constant (128 byte limit is an issue)
case 1 can work as push, except it doesn't fit there.

[Try]

Per-frame immediate data (view/proj matrix, main light)

Update on this case from OpenGothic:
updating device-local ssbo, from host-visible buffers (aka staging). Can be done cleanly by introducing cmd.update(ssbo, void*,offset, size)