Our subplot and dock rects are a but of a mess. I was trying to make the subplot bottom dock appear above the toolbar but it's really messy. After the pygfx viewport refactor we can come up with some nice hierarchical structure for our subplots and docks, and also support arbitrary layouts for figures (and maybe imgui for resizing or moving them around).

It would be great if we can get rid of docks so we reduce the number of render calls. We can probably use the overlay render for the current purpose of the docks.