* Remove SQL experimental banner and other doc adjustments.
Also,
- Adjust the ToC and other docs a bit so SQL and native queries are
presented on more equal footing.
- De-emphasize querying historicals and peons directly in the
native query docs. This is a really niche thing and may have been
confusing to include prominently in the very first paragraph.
- Remove DataSketches and Kafka indexing service from the experimental
features ToC. They are not experimental any longer and were there in
error.
* More notes.
* Slight tweak.
* Remove extra extra word.
* Remove RT node from ToC.