This reworks the integration-test-only csv testing for `metadata` to use
the `required_feature:` syntax instead of the `-IT_tests_only`
extension. This is a little more flexible and way nicer on the eyes.
Small improvements in ESQL docs and addition of examples
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Co-authored-by: Alexandros Batsakis <abatsakis@elastic.co>
Co-authored-by: Abdon Pijpelink <abdon.pijpelink@elastic.co>
* Break out 'Limitations' into separate page
* Add REST API docs
* Restructure commands, functions, and operators refs
* Add placeholder for getting started guide
* Group 'Syntax', 'Metafields', and 'MV fields' under 'Language'
* Add placeholder for Kibana page
* Add link from landing page
* Apply uniform formatting to ACOS, CASE, and DATE_PARSE function refs
* Reword default LIMIT
* Add support for COUNT(*)
* Move 'Commands' and 'Functions and operators' to individual pages
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Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
