ProjectExplorer: Move some build-related code to BuildManager

The projectexplorer.cpp file is a huge mixed bag, which could use some
cleaning up. The queue() function is very much related to the
BuildManager, so move it there.

Change-Id: Ibc6425cc27d44514803a5e7c6139f83ddd760382
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/debuggerplugin.cpp

@@ -2391,7 +2391,7 @@ void DebuggerUnitTests::testStateMachine()
     QEventLoop loop;
     connect(BuildManager::instance(), &BuildManager::buildQueueFinished,
             &loop, &QEventLoop::quit);
-    ProjectExplorerPlugin::buildProject(SessionManager::startupProject());
+    BuildManager::buildProjectWithDependencies(SessionManager::startupProject());
     loop.exec();
 
     ExecuteOnDestruction guard([] { EditorManager::closeAllEditors(false); });