Debugger: Move ownership of perspective dock widgets to plugins

Similar to the previous patch, but affecting more plugins: with dynamic
perspectives lifetime is better managed close to the code that knows how
to (re-)construct the items.

Change-Id: I0e7bfcf769d198ec2afa88b972be900baa1b6a46
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/clangtools/clangtool.cpp

@@ -98,6 +98,8 @@ ClangTool::ClangTool(const QString &name)
     m_stopAction = Debugger::createStopAction();
 }
 
+ClangTool::~ClangTool() = default;
+
 FileInfos ClangTool::collectFileInfos(Project *project, bool askUserForFileSelection) const
 {
     auto projectInfo = CppTools::CppModelManager::instance()->projectInfo(project);