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/clangcodemodel/clangcompletionassistprovider.h

@@ -28,14 +28,14 @@
 #include "clangbackendcommunicator.h"
 #include "clangcompletionassistinterface.h"
 
-#include <cpptools/cppcompletionassistprovider.h>
+#include <cppeditor/cppcompletionassistprovider.h>
 
 #include <texteditor/codeassist/assistinterface.h>
 
 namespace ClangCodeModel {
 namespace Internal {
 
-class ClangCompletionAssistProvider : public CppTools::CppCompletionAssistProvider
+class ClangCompletionAssistProvider : public CppEditor::CppCompletionAssistProvider
 {
     Q_OBJECT