Tear down the Epic Online Services SDK. Once this function has been called, no more SDK calls are permitted; calling anything after EOS_Shutdown will result in undefined behavior. EOS_Success is returned if the SDK is successfully torn down. EOS_NotConfigured is returned if a successful call to EOS_Initialize has not been made. EOS_UnexpectedError is returned if EOS_Shutdown has already been called.
An EOS_EResult is returned to indicate success or an error.