[SMS App] Make SMS character counter width only grow

SMS character counter was changing its width (both growing and
shrinking) so it also resized message field (and that caused text
reflow). This patch makes counter width only grow.

Type SMS that is long enough to make SMS character counter wider than
“Send” button. Remove the text (leave there 150 or 60 chars to keep it
visible). Character counter should keep its width.

smsapp/qml/ConversationDisplay.qml

@@ -263,6 +263,7 @@ Kirigami.ScrollablePage
                     id: "charCount"
                     text: conversationModel.getCharCountInfo(messageField.text)
                     visible: text.length > 0
+                    Layout.minimumWidth: Math.max(Layout.minimumWidth, width) // Make this label only grow, never shrink
                 }
             }
         }