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/Spotlight/SpotlightContent.qml

@@ -95,7 +95,7 @@ Item {
                 width: parent.width - 80 - Theme.spacingM
                 height: 56
                 cornerRadius: Theme.cornerRadius
-                backgroundColor: Qt.rgba(Theme.surfaceVariant.r, Theme.surfaceVariant.g, Theme.surfaceVariant.b, Theme.getContentBackgroundAlpha() * 0.7)
+                backgroundColor: Theme.surfaceContainerHigh
                 normalBorderColor: Theme.outlineMedium
                 focusedBorderColor: Theme.primary
                 leftIconName: "search"