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/autotoolsprojectmanager/autotoolsbuildsystem.h

@@ -29,7 +29,7 @@
 
 #include <projectexplorer/buildsystem.h>
 
-namespace CppTools { class CppProjectUpdater; }
+namespace CppEditor { class CppProjectUpdater; }
 
 namespace AutotoolsProjectManager {
 namespace Internal {
@@ -64,7 +64,7 @@ private:
     /// Responsible for parsing the makefiles asynchronously in a thread
     MakefileParserThread *m_makefileParserThread = nullptr;
 
-    CppTools::CppProjectUpdater *m_cppCodeModelUpdater = nullptr;
+    CppEditor::CppProjectUpdater *m_cppCodeModelUpdater = nullptr;
 };
 
 } // namespace Internal