Improve InvalidScissorRect error message

[jinleili]

Connections
#2676

Testing
Calling RenderPass set_scissor_rect with illegal arguments will output the following error message:

thread 'main' panicked at 'wgpu error: Validation Error

Caused by:
    In a RenderPass
      note: encoder = `<CommandBuffer-(0, 1, Metal)>`
    In a set_scissor_rect command
    Scissor Rect { x: 1000, y: 1000, w: 601, h: 200 } is not contained in the render target Extent3d { width: 1600, height: 1200, depth_or_array_layers: 1 }

[cwfitzgerald]

Much thanks! If you're up to it, I realize the viewport has the same issue.

[jinleili]

Okay, I can do that.