message: rpc: Add warning to user about newkeypool command
diff: @@ -359,7 +359,12 @@ RPCHelpMan keypoolrefill()
  RPCHelpMan newkeypool()
  {
  return RPCHelpMan{"newkeypool",
  - "\nEntirely clears and refills the keypool."+
  + "\nEntirely clears and refills the keypool.\n"
  + "WARNING: On non-HD wallets, this will require a new backup immediately, to include the new keys.\n"
  + "When restoring a backup of an HD wallet created before the newkeypool command is run, funds received to\n"
  + "new addresses may not appear automatically. They have not been lost, but the wallet may not find them.\n"
  + "This can be fixed by running the newkeypool command on the backup and then rescanning, so the wallet\n"
  + "re-generates the required keys." +
  HELP_REQUIRING_PASSPHRASE,
  {},
  RPCResult{RPCResult::Type::NONE, "", ""},
  