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/clangtools/clangtoolsunittests.cpp

@@ -115,9 +115,7 @@ void ClangToolsUnitTests::testProject()
 
     // Open project
     Tests::ProjectOpenerAndCloser projectManager;
-    const ProjectInfo projectInfo = projectManager.open(projectFilePath, true, m_kit);
-    const bool isProjectOpen = projectInfo.isValid();
-    QVERIFY(isProjectOpen);
+    QVERIFY(projectManager.open(projectFilePath, true, m_kit));
 
     // Run tool
     ClangTool *tool = ClangTool::instance();