Theme consistency overhaul:

- Add surface shift option, start from surface by default (previously
  was surfaceContainer). Old colors can be attained by changing it back
to "container" in theme colors
- Remove borders on surface elements, mostly
- Fix popup distances
- Use surfaceContainer/sch by default on widgets

Modules/ControlCenter/PowerMenu.qml

@@ -44,7 +44,7 @@ PanelWindow {
         radius: Theme.cornerRadius
         border.color: Qt.rgba(Theme.outline.r, Theme.outline.g,
                               Theme.outline.b, 0.08)
-        border.width: 1
+        border.width: 0
         opacity: powerMenuVisible ? 1 : 0
         scale: powerMenuVisible ? 1 : 0.85