CppTools: Turn some classes into pure value types

ProjectInfo, ProjectPart and ProjectUpdateInfo used to carry pointers
to Project and/or Toolchain, even though they were used in contexts
where these pointers were either unsafe to access or not guaranteed to
be valid anymore, which made their use difficult and error-prone.
We turn these classes into pure value types by copying in all relevant
information before the first async operation takes place.

Fixes: QTCREATORBUG-25678
Change-Id: I1914b0dbda6c7dfba6c95e5e92f2d69977755590
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/clangcodemodel/clangtextmark.cpp

@@ -88,7 +88,7 @@ ProjectExplorer::Project *projectForCurrentEditor()
 
     if (auto processor = ClangEditorDocumentProcessor::get(filePath)) {
         if (ProjectPart::Ptr projectPart = processor->projectPart())
-            return projectPart->project;
+            return projectForProjectPart(*projectPart);
     }
 
     return nullptr;