[lldb] Remove SBCommandReturnObject::ref

[teemperor]

Summary

This function was added in D67589 and returns an internal CommandReturnObject
which isn't allowed in the SB API. This patch just makes it private as all uses
of this function are inside SBCommandReturnObject.

[teemperor]

IIUC this was originally public but then we made the other users friends (but the public remained). But still putting this up for review in case I missed something

[jankratochvil]

I agree it should not be permitted to return the internal object from SB API. And if it still compiles after moving to private: then why not.

lldb/include/lldb/API/SBCommandReturnObject.h

public:
 
   const char *GetError(bool only_if_no_immediate);
 
   void SetError(lldb::SBError &error,
                 const char *fallback_error_cstr = nullptr);
 
   void SetError(const char *error_cstr);
 
-  // ref() is internal for LLDB only.
-  lldb_private::CommandReturnObject &ref() const;
-
 protected:
   friend class SBCommandInterpreter;
   friend class SBOptions;
 
   lldb_private::CommandReturnObject *operator->() const;
 
   lldb_private::CommandReturnObject *get() const;
 
   lldb_private::CommandReturnObject &operator*() const;
 
 private:
+  lldb_private::CommandReturnObject &ref() const;
+
   std::unique_ptr<lldb_private::SBCommandReturnObjectImpl> m_opaque_up;
 };
 
 } // namespace lldb
 
 #endif // LLDB_API_SBCOMMANDRETURNOBJECT_H