Split ESQL functions/operators docs files (elastic#123904) (elastic#124214)

* Port from asciidocalypse

* Fix links for operator lists

* Remove unused image files after moving/editing them

* Fix lists links

* Fix like/rlike links

* Fix remaining bad references to /elasticsearch/docs

* Fix logstash and beats references

* Fix logstash and beats references

* Fix image links

(cherry picked from commit efe7379)

Co-authored-by: Craig Taverner <[email protected]>

Author: leemthompo