mouse-test: Make some UI tweaks to follow the latest mockups

Replaces !2341 (closed)

Clicking	Scrolling

• Use "select-mode-symbolic" in the "Clicking" view switcher

• Ditch the border radius from the scroll test image

• Make click-status-emblem indicator indicator to show a more prominent green color when the test passes

• Don't use @borders for the click-status-emblems background color because this named color isn't meant for backgrounds

• Make non-green click-status-emblems dimmed

Reference: Teams/Design/settings-mockups@6d5e1813