Qt: Escape HTML when setting ElidedLabel text

ElidedLabels use Qt's rich text internally, but we need to make sure the
text we're passed via setText() is plain.

Fixes #18774

ui/qt/widgets/elided_label.cpp

@@ -74,6 +74,6 @@ void ElidedLabel::clear()
 
 void ElidedLabel::setText(const QString &text)
 {
-    full_text_ = text;
+    full_text_ = text.toHtmlEscaped();
     updateText();
 }

ui/qt/widgets/elided_label.h

@@ -46,6 +46,10 @@ public slots:
      * @brief clear Clear the label.
      */
     void clear();
+    /**
+     * @brief setText Set the label's plain text.
+     * @param text The text to set. HTML will be escaped.
+     */
     void setText(const QString &text);
 };