Python: offer to install pyside also in qml files

This shwos the same editor toolbar as in the python editor that offers
to install pyside, if the qml file can be associated to a python project
and the configured python for that project does not contain a valid
pyside.

Change-Id: Id05a2621aec9d78c4a22e61830813cd261eda4fc
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/python/pythonbuildconfiguration.h

@@ -64,6 +64,7 @@ private:
     void initialize(const ProjectExplorer::BuildInfo &info);
     void updateInterpreter(const std::optional<ProjectExplorer::Interpreter> &python);
     void updatePython(const Utils::FilePath &python);
+    void updateDocuments();
     void handlePythonUpdated(const Utils::FilePath &python);
 
     Utils::FilePath m_python;