ILocatorFilter: Introduce LocatorMatcher

This machinery is going to replace
ILocatorFilter::matchesFor() and filter usages outside
of locator scope, e.g. in find unused functions.

In contrary to LocatorWidget, which calls
Core::Internal::runSearch() in a separate thread
and the latter executes matchesFor() sequentially for all filters,
this patch offers a possibility to run all filters in parallel.

Change-Id: Ia59463c95294299090173f3d510d57c9f8c7f993
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/coreplugin.h

@@ -8,6 +8,7 @@
 
 #include <extensionsystem/iplugin.h>
 #include <utils/environment.h>
+#include <utils/futuresynchronizer.h>
 
 QT_BEGIN_NAMESPACE
 class QMenu;
@@ -46,13 +47,14 @@ public:
                            const QString &workingDirectory,
                            const QStringList &args) override;
 
+    static Utils::FutureSynchronizer *futureSynchronizer();
     static Utils::Environment startupSystemEnvironment();
     static Utils::EnvironmentItems environmentChanges();
     static void setEnvironmentChanges(const Utils::EnvironmentItems &changes);
     static QString msgCrashpadInformation();
 
 public slots:
-    void fileOpenRequest(const QString&);
+    void fileOpenRequest(const QString &);
 
 #if defined(WITH_TESTS)
 private slots:
@@ -77,6 +79,7 @@ private:
     FolderNavigationWidgetFactory *m_folderNavigationWidgetFactory = nullptr;
     Utils::Environment m_startupSystemEnvironment;
     Utils::EnvironmentItems m_environmentChanges;
+    Utils::FutureSynchronizer m_futureSynchronizer;
 };
 
 } // namespace Internal