[performance] CloseUnrelatedProjectsAction.buildConnectedComponents(IProject[]) blocks UI startup

[laeubi]

org.eclipse.ui.actions.CloseUnrelatedProjectsAction.buildConnectedComponents(IProject[]) calls the following code possibly in the UI thread:

eclipse.platform.ui/bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/actions/CloseUnrelatedProjectsAction.java

Line 83 in 0344b2b

IProject[] references = project.getReferencedProjects();

this leads to all classpath containers of all projects to be resolved what is a costly operation and blocks the whole IDE startup procedure see here:

• JDT calls PDE Classpath on startup with open Editor hindering the UI to show up eclipse-pde/eclipse.pde#1481

instead the computation should happen in the background and only the UI has to be updated once the operation succeeded.