Backport of [1]+[2] to fix tests with Qt6.8.0 and build with Qt6.8.1.

There was some refactoring in these files which prevent anything from
applying cleanly, so this was manually rebased -- hopefully correct
(fsengine tests pass again, so it should be fine).

[1] https://github.com/qt-creator/qt-creator/commit/81d4e8a3742
[2] https://github.com/qt-creator/qt-creator/commit/f993fb76ded
--- a/src/libs/utils/fsengine/diriterator.h
+++ b/src/libs/utils/fsengine/diriterator.h
@@ -16,4 +16,36 @@
 namespace Internal {
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+inline std::pair<QDir::Filters, QDirIterator::IteratorFlags> convertQDirListingIteratorFlags(
+    QDirListing::IteratorFlags flags)
+{
+    QDir::Filters filters = QDir::Files | QDir::Dirs | QDir::System | QDir::NoDotAndDotDot;
+    QDirIterator::IteratorFlags iteratorFlags = QDirIterator::NoIteratorFlags;
+
+    if (flags & QDirListing::IteratorFlag::ExcludeFiles)
+        filters.setFlag(QDir::Files, false);
+    if (flags & QDirListing::IteratorFlag::ExcludeDirs)
+        filters.setFlag(QDir::Dirs, false);
+    if (flags & QDirListing::IteratorFlag::ExcludeSpecial)
+        filters.setFlag(QDir::System, false);
+    if (flags & QDirListing::IteratorFlag::CaseSensitive)
+        filters.setFlag(QDir::CaseSensitive, true);
+    if (flags & QDirListing::IteratorFlag::IncludeHidden)
+        filters.setFlag(QDir::Hidden, true);
+
+    if (flags & QDirListing::IteratorFlag::IncludeDotAndDotDot) {
+        filters.setFlag(QDir::NoDot, false);
+        filters.setFlag(QDir::NoDotDot, false);
+    }
+
+    if (flags & QDirListing::IteratorFlag::Recursive)
+        iteratorFlags.setFlag(QDirIterator::Subdirectories, true);
+    if (flags & QDirListing::IteratorFlag::FollowDirSymlinks)
+        iteratorFlags.setFlag(QDirIterator::FollowSymlinks, true);
+
+    return {filters, iteratorFlags};
+}
+#endif
+
 class DirIterator : public QAbstractFileEngineIterator
 {
--- a/src/libs/utils/fsengine/fixedlistfsengine.h
+++ b/src/libs/utils/fsengine/fixedlistfsengine.h
@@ -67,8 +67,14 @@
 
 #if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
-    IteratorUniquePtr beginEntryList(const QString &path,
-                                     QDir::Filters filters,
-                                     const QStringList &filterNames) override
+    QAbstractFileEngine::IteratorUniquePtr beginEntryList(
+        const QString &path,
+        QDirListing::IteratorFlags itFlags,
+        const QStringList &filterNames) override
     {
+        // We do not support recursive or following symlinks for the Fixed List engine.
+        Q_ASSERT(itFlags.testFlag(QDirListing::IteratorFlag::Recursive) == false);
+
+        const auto [filters, _] = convertQDirListingIteratorFlags(itFlags);
+
         return std::make_unique<DirIterator>(m_children, path, filters, filterNames);
     }
--- a/src/libs/utils/fsengine/fsengine_impl.cpp
+++ b/src/libs/utils/fsengine/fsengine_impl.cpp
@@ -297,11 +297,25 @@
 
 #if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
-QAbstractFileEngine::IteratorUniquePtr FSEngineImpl::beginEntryList(const QString &path,
-                                                                    QDir::Filters filters,
-                                                                    const QStringList &filterNames)
+QAbstractFileEngine::IteratorUniquePtr FSEngineImpl::beginEntryList(
+    const QString &path, QDirListing::IteratorFlags itFlags, const QStringList &filterNames)
+{
+    const auto [filters, iteratorFlags] = convertQDirListingIteratorFlags(itFlags);
+
+    FilePaths paths{m_filePath.pathAppended(".")};
+    m_filePath.iterateDirectory(
+        [&paths](const FilePath &p, const FilePathInfo &fi) {
+            paths.append(p);
+            FilePathInfoCache::CachedData *data
+                = new FilePathInfoCache::CachedData{fi, QDateTime::currentDateTime().addSecs(60)};
+            g_filePathInfoCache.cache(p, data);
+            return IterationPolicy::Continue;
+        },
+        {filterNames, filters, iteratorFlags});
+
+    return std::make_unique<DirIterator>(std::move(paths), path, filters, filterNames);
+}
 #else
 QAbstractFileEngine::Iterator *FSEngineImpl::beginEntryList(QDir::Filters filters,
                                                             const QStringList &filterNames)
-#endif
 {
     FilePaths paths{m_filePath.pathAppended(".")};
@@ -317,10 +331,7 @@
         {filterNames, filters});
 
-#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
-    return std::make_unique<DirIterator>(std::move(paths), path, filters, filterNames);
-#else
     return new DirIterator(std::move(paths));
-#endif
 }
+#endif
 
 qint64 FSEngineImpl::read(char *data, qint64 maxlen)
--- a/src/libs/utils/fsengine/fsengine_impl.h
+++ b/src/libs/utils/fsengine/fsengine_impl.h
@@ -60,7 +60,10 @@
 
 #if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
-    IteratorUniquePtr beginEntryList(const QString &path, QDir::Filters filters,
-                                     const QStringList &filterNames) override;
-    IteratorUniquePtr endEntryList() override { return {}; }
+    IteratorUniquePtr beginEntryList(
+        const QString &path,
+        QDirListing::IteratorFlags filters,
+        const QStringList &filterNames) final;
+
+    IteratorUniquePtr endEntryList() final { return {}; }
 #else
     Iterator *beginEntryList(QDir::Filters filters, const QStringList &filterNames) override;
--- a/src/libs/utils/fsengine/fsenginehandler.cpp
+++ b/src/libs/utils/fsengine/fsenginehandler.cpp
@@ -23,7 +23,8 @@
 public:
 #if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
-    IteratorUniquePtr beginEntryList(const QString &path,
-                                     QDir::Filters filters,
-                                     const QStringList &filterNames) override
+    IteratorUniquePtr beginEntryList(
+        const QString &path,
+        QDirListing::IteratorFlags filters,
+        const QStringList &filterNames) override
     {
         return std::make_unique<FileIteratorWrapper>(