TextEditor: Dissolve QuickFixAssistProcessor

... into QuickFixAssistProcessor and QmlJSQuickFixAssistProcessor,
by essentially duplicating the class, but moving the actual work to
a new a GenericProposal::createProposal(...QuickFixOperations...)

Less indirection, and less code in total.

Change-Id: I2f8cba970bf587c9cbf04321269a60ed51bfae2a
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/qmljseditor/qmljsquickfix.h

@@ -90,8 +90,6 @@ protected:
         QmlJSQuickFixOperation objects.
      */
     virtual void match(const QmlJSQuickFixInterface &interface, TextEditor::QuickFixOperations &result) = 0;
-
-    static QList<QuickFixFactory *> qmlJSQuickFixFactories();
 };
 
 } // namespace QmlJSEditor