Different rect shading options.

Opacity mode:
- SF layer rects, WM window states and VC views that are visible have an opacity reflected by their alpha

Still kept shading modes as optional in rects component, as input may wish to have different shading modes.

Final screencast: https://screencast.googleplex.com/cast/NDg1NjIxMjgwNDg2MTk1MnwxMjc3OTIyZS1kNw

Fixes: 339435186
Test: npm run test:unit:ci

Change-Id: Ic2950a485cd9dfacbcf6cacaa55abc3e8079e3f0
22 files changed