Move PersistentParserState onto SourceFile

Move the global PersistentParserState from
the CompilerInstance to the source file that code
completion is operating on, only hooking up the
state when it's needed. This will help make it
easier to requestify source file parsing.

tools/SourceKit/lib/SwiftLang/SwiftConformingMethodList.cpp

@@ -42,8 +42,8 @@ static bool swiftConformingMethodListImpl(
             ide::makeConformingMethodListCallbacksFactory(ExpectedTypeNames,
                                                           Consumer));
 
-        performCodeCompletionSecondPass(CI.getPersistentParserState(),
-                                        *callbacksFactory);
+        auto SF = CI.getCodeCompletionFile();
+        performCodeCompletionSecondPass(*SF.get(), *callbacksFactory);
       });
 }