Indication that filter aggregation is using Lucene (not KQL)

[AlonaNadler]

While we are moving to KQL by default in 7.0, there are still areas which . will be queried only with Lucene like filter aggregations in Visualize and filter in TSVB (group by filter, ratio filter, and panel filters)
The concern with TSVB and Visualize filter aggregation is different, users often copy paste their search bar query into the filter aggregations, in that case, they will get errors. We are adding indications in the query bar but not in filter aggregation.
Short term resolution is to add placeholder text in the filter aggregation Lucene, as a temporary solution, otherwise users can start troubleshooting for a while until realize what is the issue

Longer term KQL will work on filter aggregation as well #29790

[elasticmachine]

Pinging @elastic/kibana-app