The scissor can be used to efficiently clip draws to an integer rectangle on the framebuffer.

Allow the user to set the scissor on the RenderPass by passing in a Scissor class that just stores an integer rectangle.

There is no need to add functionality to "disable" the scissor. By default, the scissor is set to the render target texture size. So if the user wants to "disable" the scissor, they should simply call setScissor again and set it back to the render target texture size.