[tiny-skia] Changes affected to `shadows` needs to have full redraw

[T-256]

Is your issue REALLY a bug?

• My issue is indeed a bug!
• I am not crazy! I will not fill out this form just to ask a question or request a feature. Pinky promise.

Is there an existing issue for this?

• I have searched the existing issues.

Is this issue related to iced?

• My hardware is compatible and my graphics drivers are up-to-date.

What happened?

By using tiny-skia backend, try to apply a change to a shadow (e.g. hover mouse over button with shadow), it seems it renders incorrectly.
You can also run custom_quad from examples folder with set ICED_BACKEND=tiny-skia.

Note that if it would solve by redrawing whole window. try resizing window to trigger full redraw event.

What is the expected behavior?

It should be as same as wgpu.

Version

master

Operating System

Windows

Do you have any log output?

No response