Provide hold_forever sink to help with testing and experimenting

Is your feature request related to a problem? Please describe.

Sometimes when running data through Data Prepper, I'd like to test the behavior when data is not sent to a sink.

Describe the solution you'd like

Provide a new sink - hold_forever.

sink:
- hold_forever:

This sink would not send the data, would not acknowledge to acknowledgements.

This sink could provide a warning that this is only for testing purposes.

Describe alternatives you've considered (Optional)

It would be interesting to consider having a CLI flag for debugMode. Then when this flag is provided, this sink would be available. If it isn't provided, the sink is unavailable. This could prevent misuse of it.

However, Data Prepper's current arguments are not very robust. So I'd like to propose that something like this come later.

Additional context

I already have this implemented and keep it in my development environment. But, it may be useful beyond this, so I'd like to make it part of the standard sinks.