HackStudio: Integate with C++ parser-based autocomplete

By default, C++ auto completion will still be performed by the
lexer-based logic.
However, the parser-based logic can be switched on via the menubar.

Userland/DevTools/HackStudio/LanguageServers/Cpp/CMakeLists.txt

@@ -1,7 +1,8 @@
 set(SOURCES
     ClientConnection.cpp
     main.cpp
-    AutoComplete.cpp
+    LexerAutoComplete.cpp
+    ParserAutoComplete.cpp
 )
 
 set(GENERATED_SOURCES