CMake: make project file system tree scanner persistent

Project source tree is a same for all build configurations so it is
a good idea to keep it persistent between CMake runs, configurations
switches and so on. It safes a lot of time for big projects.

Move more operations to the scanner thread:
 - Nodes filtering: skip .user files on top level of the project, skip
well-known extensions and octet-streams: In most cases these are not
required to be shown in the project tree.
 - Nodes sorting

Fix small memory leak: we have .user in the scanner result. After this
node filtered out, but is not feed (old code at the
BuildDirManager::generateProjectTree()). Now .user file skips during scan
without memory allocation at all.

Allow user manually rescan project tree by call Build -> Rescan project
tree. It runs CMake and Tree Scanner together: in most cases only CMake
run requires but time to time (VCS update) full rescan also required.

Change-Id: I4a6e6c897202da557509291c79932dd7751860e5
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cmakeprojectmanager/builddirmanager.h

@@ -30,7 +30,6 @@
 
 #include <utils/fileutils.h>
 
-#include <QFutureWatcher>
 #include <QObject>
 #include <QTemporaryDir>
 #include <QTimer>
@@ -72,7 +71,7 @@ public:
     bool updateCMakeStateBeforeBuild();
     bool persistCMakeState();
 
-    void generateProjectTree(CMakeListsNode *root);
+    void generateProjectTree(CMakeListsNode *root, const QList<ProjectExplorer::FileNode *> &allFiles);
     QSet<Core::Id> updateCodeModel(CppTools::ProjectPartBuilder &ppBuilder);
 
     QList<CMakeBuildTarget> buildTargets() const;
@@ -103,8 +102,6 @@ private:
 
     void becameDirty();
 
-    void asyncScanForFiles(QFutureInterface<QList<ProjectExplorer::FileNode *>> *fi);
-
     CMakeBuildConfiguration *m_buildConfiguration = nullptr;
     mutable std::unique_ptr<QTemporaryDir> m_tempDir = nullptr;
     mutable CMakeConfig m_cmakeCache;
@@ -112,8 +109,6 @@ private:
     QTimer m_reparseTimer;
 
     std::unique_ptr<BuildDirReader> m_reader;
-    QFutureWatcher<QList<ProjectExplorer::FileNode*>> m_futureWatcher;
-    QFuture<QList<ProjectExplorer::FileNode*>> m_scanFuture;
 
     mutable QList<CMakeBuildTarget> m_buildTargets;
 };