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/Components/PowerOptionsPane.qml

@@ -18,10 +18,7 @@ Item {
         width: parent.width
         height: 60
         radius: Theme.cornerRadius
-        color: Qt.rgba(Theme.surfaceVariant.r,
-                       Theme.surfaceVariant.g,
-                       Theme.surfaceVariant.b,
-                       Theme.getContentBackgroundAlpha() * 0.4)
+        color: Theme.surfaceContainerHigh
         border.color: Qt.rgba(Theme.outline.r, Theme.outline.g,
                               Theme.outline.b, 0.08)
         border.width: root.expanded ? 1 : 0