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/clangselectablefilesdialog.h

@@ -47,7 +47,7 @@ class SelectableFilesDialog : public QDialog
     Q_OBJECT
 
 public:
-    explicit SelectableFilesDialog(const CppTools::ProjectInfo &projectInfo,
+    explicit SelectableFilesDialog(ProjectExplorer::Project *project,
                                    const FileInfoProviders &fileInfoProviders,
                                    int initialProviderIndex);
     ~SelectableFilesDialog() override;