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

Modals/Settings/PowerSettings.qml

@@ -31,7 +31,7 @@ Item {
                 radius: Theme.cornerRadius
                 color: Qt.rgba(Theme.surfaceVariant.r, Theme.surfaceVariant.g, Theme.surfaceVariant.b, 0.3)
                 border.color: Qt.rgba(Theme.outline.r, Theme.outline.g, Theme.outline.b, 0.2)
-                border.width: 1
+                border.width: 0
 
                 Column {
                     id: timeoutSection