Processor to filter out (remove/drop) entire events

[dlvenable]

Data Prepper should provide a processor which removes entire events. This processor need not take any special input, but does require conditional support from #522. (Otherwise every event would be dropped).

Outstanding Questions

What name should this processor have?

[graytaylor0]

drop seems fine but drop_events might be a little better.

[dlvenable]

I agree on drop_events. It is much clearer on what it does, since it could be unclear as to whether it drops events or specific fields.