ProjectNodes: Handle supported actions one-by-one

Getting the full list for a node can get quite expensive e.g. in
cases of recursive calls of QMakeProjectManager::findPriFile.

However, the FlatModel needs to decide quickly on whether an item
is editable to potentially allow renaming.

So split up QList<Actions> supportedActions() into individual
bool supportsAction(action) calls and make sure Rename is not
on the critical path.

Task-number: QTCREATORBUG-17953
Change-Id: I31841847f8aa7d7b94c63d76ce71efb1c930fa69
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/pythoneditor/pythoneditorplugin.cpp

@@ -122,11 +122,7 @@ public:
     PythonProjectNode(PythonProject *project);
 
     bool showInSimpleTree() const override;
-
-    QList<ProjectAction> supportedActions(Node *node) const override;
-
     QString addFileFilter() const override;
-
     bool renameFile(const QString &filePath, const QString &newFilePath) override;
 
 private:
@@ -655,13 +651,6 @@ bool PythonProjectNode::showInSimpleTree() const
     return true;
 }
 
-QList<ProjectAction> PythonProjectNode::supportedActions(Node *node) const
-{
-    Q_UNUSED(node);
-    //return { AddNewFile, AddExistingFile, AddExistingDirectory, RemoveFile, Rename };
-    return {};
-}
-
 QString PythonProjectNode::addFileFilter() const
 {
     return QLatin1String("*.py");