R1:287e708c4d3e

Adjust and wordsmith Search documentation

Summary:
Ref T12450. General adjustments:

- Try to make "Cluster: Search" more about "stuff in common + types" instead of pretty much all being Elastic-specific, so we can add Solr or whatever later.
- Provide guidance about rebuilding indexes after making a change.
- Simplify the basic examples, then provide a more advanced example at the ed.
- Really try to avoid suggesting anyone configure Elasticsearch ever for any reason.

Test Plan: Read documents…