Debugger: Remove some uses of semi-global currentEngine()

Make use of recent TreeModel improvements in various
tool views, push more operations into the engine-
owned data models, specifically context menu creation.

Change-Id: I479c97102b9fb81611c6461c6df1cec59295179a
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/sourcefileshandler.h

@@ -31,12 +31,14 @@
 namespace Debugger {
 namespace Internal {
 
+class DebuggerEngine;
+
 class SourceFilesHandler : public QAbstractItemModel
 {
     Q_OBJECT
 
 public:
-    SourceFilesHandler();
+    explicit SourceFilesHandler(DebuggerEngine *engine);
 
     int columnCount(const QModelIndex &parent) const
         { return parent.isValid() ? 0 : 2; }
@@ -47,6 +49,7 @@ public:
         { return createIndex(row, column); }
     QVariant headerData(int section, Qt::Orientation orientation, int role) const;
     QVariant data(const QModelIndex &index, int role) const;
+    bool setData(const QModelIndex &idx, const QVariant &data, int role) override;
     Qt::ItemFlags flags(const QModelIndex &index) const;
 
     void clearModel();
@@ -57,6 +60,7 @@ public:
     QAbstractItemModel *model() { return m_proxyModel; }
 
 private:
+    DebuggerEngine *m_engine;
     QStringList m_shortNames;
     QStringList m_fullNames;
     QAbstractItemModel *m_proxyModel;