[AFV] Ref T739, remove implementation details from IContextAudio to keep the DBus interface "pure"

* This was an approach to avoid registration of "local signals"
* that part DID NOT work as planned, as all object's signals are registered
* the refactoring itself nevertheless is NOT a bad idea and has been kept
* as the audio context has this special "concept" and CAfvClient can run on both sides (proxy AND impl.side)

src/blackcore/context/context.cpp

@@ -18,7 +18,7 @@ namespace BlackCore
     {
         const CLogCategoryList &IContext::getLogCategories()
         {
-            static const BlackMisc::CLogCategoryList cats { BlackMisc::CLogCategory::context() };
+            static const CLogCategoryList cats { BlackMisc::CLogCategory::context() };
             return cats;
         }