refactor: update display mode icons and logic

1. Changed icon names from 'osd_display_*' to 'osd_multi_screen_*' for
better consistency
2. Modified display mode logic to support more than 2 screens by:
   - Always sorting output names (not just for 2 screens)
   - Using 'osd_multi_screen_only_more' icon when more than 2 screens
exist
3. Removed old icon files and added new ones with updated naming scheme

refactor: 更新显示模式图标和逻辑

1. 将图标名称从'osd_display_*'改为'osd_multi_screen_*'以提高一致性
2. 修改显示模式逻辑以支持超过2个屏幕：
   - 始终排序输出名称（不仅限于2个屏幕时）
   - 当存在超过2个屏幕时使用'osd_multi_screen_only_more'图标
3. 删除旧图标文件并添加具有更新命名方案的新图标

pms: BUG-315934

Author: 18202781743

panels/notification/osd/displaymode/displaymodeapplet.cpp

@@ -165,13 +165,14 @@ void DisPlayModeApplet::fetchPlanItems()
     m_planItems.clear();
     m_currentPlanItem = nullptr;
 
-    m_planItems << new DPItem(tr("Duplicate"), "osd_display_copy", DPItem::Merge, this);
-    m_planItems << new DPItem(tr("Extend"), "osd_display_expansion", DPItem::Extend, this);
-    if (outputNames.size() == 2) {
-        std::sort(outputNames.begin(), outputNames.end(), std::greater<QString>());
+    m_planItems << new DPItem(tr("Duplicate"), "osd_multi_screen_copy", DPItem::Merge, this);
+    m_planItems << new DPItem(tr("Extend"), "osd_multi_screen_extension", DPItem::Extend, this);
+    std::sort(outputNames.begin(), outputNames.end(), std::greater<QString>());
+    if (outputNames.size() > 1) {
         for (int i = 0; i < outputNames.size(); i++) {
             const auto item = outputNames[i];
-            m_planItems << new DPItem(tr("Only on %1").arg(item), item, QString("osd_display_custom%1").arg(i + 1), DPItem::Single, this);
+            const QString iconName = i < 2 ? QString("osd_multi_screen_only%1").arg(i + 1) : "osd_multi_screen_only_more";
+            m_planItems << new DPItem(tr("Only on %1").arg(item), item, iconName, DPItem::Single, this);
         }
     }
 }