AutoTest: Free TestTreeItem from CppTools dependency

Makes TestTreeItem programming language agnostic.

By moving the "query" methods to CppTools, the cohesion within these
methods is improved, i.e. information crosses the AutoTest <-> CppTools
border fewer times. Furthermore, it allows the CppTools plugin to see
how its data is being used, allowing it to optimize its queries
behind the scenes.

Change-Id: I0a60140abaca1193d500605dfa2812b4d937d94c
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cpptools/cppmodelmanager.h

@@ -230,6 +230,14 @@ public:
     Core::IFindFilter *symbolsFindFilter() const;
     Core::ILocatorFilter *currentDocumentFilter() const;
 
+    /*
+     * try to find build system target that depends on the given file - if the file is no header
+     * try to find the corresponding header and use this instead to find the respective target
+     */
+    QSet<QString> dependingInternalTargets(const QString &file) const;
+
+    QSet<QString> internalTargets(const QString &filePath) const;
+
     void renameIncludes(const QString &oldFileName, const QString &newFileName);
 
     // for VcsBaseSubmitEditor