Add exclude_keys option to KV processor

[andrewkroh]

It would be nice to have an exclude_keys configuration option for the key-value processor in Ingest Node. exclude_keys would specify a list of keys that are not included in the final document even if they are present in the raw data parsed by the processor. There is already an include_keys filter.

The kv filter in Logstash has this option.

I want to use this to prevent certain keys from being overwritten by dynamic data coming from the KV processor.

[javanna]

@talevy what do you think?

[talevy]

this makes sense, I'll get to it soon!