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.cpp

@@ -313,6 +313,12 @@ QObject *CorePlugin::remoteCommand(const QStringList & /* options */,
     return res;
 }
 
+FutureSynchronizer *CorePlugin::futureSynchronizer()
+{
+    QTC_ASSERT(m_instance, return nullptr);
+    return &m_instance->m_futureSynchronizer;
+}
+
 Environment CorePlugin::startupSystemEnvironment()
 {
     return m_instance->m_startupSystemEnvironment;