QmlDesigner: Fix the build error for CollectionEditor

* fixes the gcc build error on CollectionEditorUtils
* fixes the unused parameters error on macOS
* fixes the build error for using the unknown template for QPointer

Change-Id: I71f6fe319b5b682b858712139084d26079a822fb
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>
Reviewed-by: Qt CI Patch Build Bot <ci_patchbuild_bot@qt.io>
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>

src/plugins/qmldesigner/components/collectioneditor/collectiondetailssortfiltermodel.cpp

@@ -64,8 +64,8 @@ bool CollectionDetailsSortFilterModel::selectColumn(int column)
 
 CollectionDetailsSortFilterModel::~CollectionDetailsSortFilterModel() = default;
 
-bool CollectionDetailsSortFilterModel::filterAcceptsRow(int sourceRow,
-                                                        const QModelIndex &sourceParent) const
+bool CollectionDetailsSortFilterModel::filterAcceptsRow(
+    [[maybe_unused]] int sourceRow, [[maybe_unused]] const QModelIndex &sourceParent) const
 {
     return true;
 }

src/plugins/qmldesigner/components/collectioneditor/collectiondetailssortfiltermodel.h

@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include <QPointer>
 #include <QSortFilterProxyModel>
 
 namespace QmlDesigner {

src/plugins/qmldesigner/components/collectioneditor/collectioneditorutils.cpp

@@ -12,6 +12,11 @@ namespace {
 
 using CollectionDataVariant = std::variant<QString, bool, double, QUrl, QColor>;
 
+inline bool operator<(const QColor &a, const QColor &b)
+{
+    return a.name(QColor::HexArgb) < b.name(QColor::HexArgb);
+}
+
 inline CollectionDataVariant valueToVariant(const QVariant &value,
                                             QmlDesigner::CollectionDetails::DataType type)
 {
@@ -45,12 +50,6 @@ struct LessThanVisitor
     {
         return a < b;
     }
-
-    template<>
-    bool operator()(const QColor &a, const QColor &b) const
-    {
-        return a.name(QColor::HexArgb) < b.name(QColor::HexArgb);
-    }
 };
 
 } // namespace