[docs] Generated reference docs for ES helpers are incomplete

[Reference docs for ES helpers](https://www.elastic.co/docs/reference/elastic-cli/cli/stack/es/helpers) does not show the sub-commands we would expect to see: `scroll-search`, `bulk-ingest`, `msearch` and `watch`.

I presume this is due to them being generated incorrectly by `elastic cli-schema`.

Start with the generated ES helpers reference page and inspect how `elastic cli-schema` produces it. Trace why `scroll-search`, `bulk-ingest`, `msearch`, and `watch` are omitted, then regenerate the reference docs and confirm all four sub-commands appear.

Written by the indexing model from the issue text.