Adwaita: Try to fix up selection touch handles

Adwaita: Try to fix up selection touch handles

The text handles reuse the style context from their parent widget,
and just add .cursor-handle. That means that the more specific
entry selectors override the .cursor-handle theming unless we
select for .entry.cursor-handle. We also need to work harder to
keep the .entry styling from drawing decorations around the outlines.