Merge CppTools into CppEditor

There was no proper separation of responsibilities between these
plugins. In particular, CppTools had lots of editor-related
functionality, so it's not clear why it was separated out in the first
place.
In fact, for a lot of code, it seemed quite arbitrary where it was put
(just one example: switchHeaderSource() was in CppTools, wheras
switchDeclarationDefinition() was in CppEditor).
Merging the plugins will enable us to get rid of various convoluted
pseudo-abstractions that were only introduced to keep up the artificial
separation.

Change-Id: Iafc3bce625b4794f6d4aa03df6cddc7f2d26716a
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/autotest/qtest/qttestparser.h

@@ -32,7 +32,7 @@
 
 #include <utils/optional.h>
 
-namespace CppTools { class CppModelManager; }
+namespace CppEditor { class CppModelManager; }
 
 namespace Autotest {
 namespace Internal {
@@ -62,7 +62,7 @@ public:
                          const Utils::FilePath &fileName) override;
 
 private:
-    TestCases testCases(const CppTools::CppModelManager *modelManager,
+    TestCases testCases(const CppEditor::CppModelManager *modelManager,
                         const Utils::FilePath &fileName) const;
     QHash<QString, QtTestCodeLocationList> checkForDataTags(const Utils::FilePath &fileName) const;
     struct TestCaseData {