ProjectExplorer: Handle project file list globally

Handle the generation of the list of files in a project globally, based
on the project tree.

Creator now has the concept of TreeManagers which can enrich the project
tree with additional data (e.g. the files found in a resource file), which
the project does not necessarily know about. So use that tree to find
the files that belong to a project instead of implementing similar features
in each project.

Change-Id: Ia375a914a1f2c0adaa427f9eda834eec2db07f68
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Marco Benelli <marco.benelli@qt.io>

src/plugins/autotoolsprojectmanager/autotoolsproject.cpp

@@ -101,12 +101,6 @@ QString AutotoolsProject::defaultBuildDirectory(const QString &projectPath)
     return QFileInfo(projectPath).absolutePath();
 }
 
-QStringList AutotoolsProject::files(FilesMode fileMode) const
-{
-    Q_UNUSED(fileMode);
-    return m_files;
-}
-
 // This function, is called at the very beginning, to
 // restore the settings if there are some stored.
 Project::RestoreResult AutotoolsProject::fromMap(const QVariantMap &map, QString *errorMessage)