Don't call DocumentManager::addDocument() from non-main thread

Detect that constructor of ResourceTopLevelNode is being
run from non-main thread and omit creation of ResourceFileWatcher
in this case. The construction of ResourceFileWatcher
will be postponed until the node tree returns back
to the main thread. This happens later inside
Project::setRootProjectNode() when ProjectTree::applyTreeManager()
is called for the second time - this time it's done from the main
thread. In order to setup the lacking resource file watchers
we install an additional folder node visitor only in case when
the handler is called from main thread. The visitor
sets up the lacking resource watchers if that's still needed.

Amends: 0bcab32657

Fixes: QTCREATORBUG-26417
Change-Id: Ia1bfb7f284afb833b6b4291accc4d0a91bd0d6c5
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cmakeprojectmanager/fileapidataextractor.cpp

@@ -757,7 +757,7 @@ FileApiQtcData extractData(FileApiData &input,
     result.projectParts = generateRawProjectParts(data, sourceDirectory, buildDirectory);
 
     auto rootProjectNode = generateRootProjectNode(data, sourceDirectory, buildDirectory);
-    ProjectTree::applyTreeManager(rootProjectNode.get()); // QRC nodes
+    ProjectTree::applyTreeManager(rootProjectNode.get(), ProjectTree::AsyncPhase); // QRC nodes
     result.rootProjectNode = std::move(rootProjectNode);
 
     setupLocationInfoForTargets(result.rootProjectNode.get(), result.buildTargets);