This primarily splits the old preview:true warning from the newer applies_to approach. Since all of our current applies_to examples are actually just behaviour modifications of current functions, we do not use the official docs {applies_to} syntax. However there is code to make use of that in the case where we have an entirely new function which will appear in a new version.
Co-authored-by: Alexander Spies <alexander.spies@elastic.co>
Manual backport of two PRs: * #125155 * #125251
Even though the docs are not needed in 9.0, due to all docs being
published off main, doing the backport makes future backports of
non-docs, but docs-adjacent PRs easier.
This entirely syncs the contents of docs/reference/query-languages/esql with main, just so we can continue auto-backporting easily, which will continue to be relevant.
