CppEditor: Improve "definition from declaration" for templates

- Make sure the template parameters are included in the definition.
- Find the correct insertion location when using an already-defined
  template member function as an anchor.

Fixes: QTCREATORBUG-24848
Change-Id: I1272ba36403904e7aed81bcef48745793c5e2217
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cppeditor/cppquickfixes.cpp

@@ -3040,6 +3040,7 @@ public:
         oo.showReturnTypes = true;
         oo.showArgumentNames = true;
         oo.showEnclosingTemplate = true;
+        oo.showTemplateParameters = true;
 
         if (defPos == DefPosInsideClass) {
             const int targetPos = targetFile->position(loc.line(), loc.column());