CppEditor: Generalize CppUseSelectionsUpdater

Let CppUseSelectionsUpdater delegate the work to
*EditorDocumentProcessor so that the clang code model can also provide
results.

Change-Id: I6872afbfeea1a5c4a64fdf19fcb1992f134dde08
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/cpptools/baseeditordocumentprocessor.h

@@ -26,6 +26,7 @@
 #pragma once
 
 #include "baseeditordocumentparser.h"
+#include "cppcursorinfo.h"
 #include "cppsemanticinfo.h"
 #include "cpptools_global.h"
 
@@ -72,6 +73,8 @@ public:
 
     virtual void setParserConfig(const BaseEditorDocumentParser::Configuration config);
 
+    virtual QFuture<CursorInfo> cursorInfo(const CursorInfoParams &params) = 0;
+
 public:
     using HeaderErrorDiagnosticWidgetCreator = std::function<QWidget*()>;