Track down set_scissor_rect issue

[ecton]

From khonsulabs/cushy#93, on the GL backend, set_scissor_rect on the Drawing type somehow gets stuck on the final rect, preventing all widgets except the final to be clipped. I added a set_scissor_rect to the full dimensions of the view in RenderingGraphics::drop.

By set_scissor_rect's documentation, it should only impact drawing calls being performed after the call. Yet, this workaround is calling set_scissor_rect right before the RenderPass is dropped, therefore there are literally no remaining draw calls to be performed. Yet, it works around the issue.

This issue is to try to minimize an example that reproduces it. My attempts so far have been fruitless. It may require switching between multiple bind groups or push constants, as my attempts to create a simple example without those has been fruitless.