Debugger: Merge QmlInspectorAdapter into QmlInspectorAgent

There's a 1:1 relation, and the abstraction is not needed anymore.

Also remove some unused code.

Change-Id: I09a2522deb5d522f46ec7518d19978a038032fbb
Reviewed-by: Ulf Hermann <ulf.hermann@theqtcompany.com>

src/plugins/debugger/qml/qml.pri

@@ -4,13 +4,11 @@ HEADERS += \
     $$PWD/qmlcppengine.h \
     $$PWD/interactiveinterpreter.h \
     $$PWD/qmlv8debuggerclientconstants.h \
-    $$PWD/qmlinspectoragent.h \
-    $$PWD/qmlinspectoradapter.h
+    $$PWD/qmlinspectoragent.h
 
 SOURCES += \
     $$PWD/qmlengine.cpp \
     $$PWD/qmlengineutils.cpp \
     $$PWD/qmlcppengine.cpp \
     $$PWD/interactiveinterpreter.cpp \
-    $$PWD/qmlinspectoragent.cpp \
-    $$PWD/qmlinspectoradapter.cpp
+    $$PWD/qmlinspectoragent.cpp