[NFC] Refactor getRenameDecl to use the request evaluator

Move `getRenameDecl` from `PrintAsObjC` into its own request so that
other components can re-use this functionality.

include/swift/AST/Module.h

@@ -774,7 +774,6 @@ public:
   void collectBasicSourceFileInfo(
       llvm::function_ref<void(const BasicSourceFileInfo &)> callback) const;
 
-public:
   /// Retrieve a fingerprint value that summarizes the contents of this module.
   ///
   /// This interface hash a of a module is guaranteed to change if the interface
@@ -787,6 +786,15 @@ public:
   /// contents have been made.
   Fingerprint getFingerprint() const;
 
+  /// Returns an approximation of whether the given module could be
+  /// redistributed and consumed by external clients.
+  ///
+  /// FIXME: The scope of this computation should be limited entirely to
+  /// RenamedDeclRequest. Unfortunately, it has been co-opted to support the
+  /// \c SerializeOptionsForDebugging hack. Once this information can be
+  /// transferred from module files to the dSYMs, remove this.
+  bool isExternallyConsumed() const;
+
   SourceRange getSourceRange() const { return SourceRange(); }
 
   static bool classof(const DeclContext *DC) {