QmlDesigner: Fix 32 bit

Because std::ptrdiff_t and int are the same under 32 bit the constructor
is changed to a template. The class is private so it is very unlikely
that it leads to errors.

Task-number: QTCREATORBUG-26910
Change-Id: I94c987b9b6d2f04876740ff283a339c0db056cfd
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Christophe Giboudeaux <christophe@krop.fr>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/qmldesigner/designercore/projectstorage/storagecache.h

@@ -67,15 +67,8 @@ class StorageCache
 
         StorageCacheIndex(const char *) = delete;
 
-        constexpr explicit StorageCacheIndex(int id) noexcept
-            : id{id}
-        {}
-
-        constexpr explicit StorageCacheIndex(std::size_t id) noexcept
-            : id{static_cast<int>(id)}
-        {}
-
-        constexpr explicit StorageCacheIndex(std::ptrdiff_t id) noexcept
+        template<typename IntegerType>
+        constexpr explicit StorageCacheIndex(IntegerType id) noexcept
             : id{static_cast<int>(id)}
         {}