Refine mobileform settings

Numerous refinements to the new mobileform setting pages 
- Ensure left and right padding at the top level is 0 for mobile
- Centre align the avatar in the account editor page and add tooltip to button
- Fix the bubble/compact mode setting so that it fits when thin, i.e on mobile
- Fix the loading placeholder in device settings

src/qml/Settings/ThemeRadioButton.qml

@@ -15,11 +15,12 @@ QQC2.RadioButton {
     implicitHeight: contentItem.implicitHeight
 
     property alias innerObject: contentLayout.children
+    property bool thin
 
     contentItem: ColumnLayout {
         Kirigami.ShadowedRectangle {
             implicitWidth: implicitHeight * 1.6
-            implicitHeight: Kirigami.Units.gridUnit * 6
+            implicitHeight: delegate.thin ? Kirigami.Units.gridUnit * 5 : Kirigami.Units.gridUnit * 6
             radius: Kirigami.Units.smallSpacing
             Kirigami.Theme.inherit: false
             Kirigami.Theme.colorSet: Kirigami.Theme.View