Autogenerate markdown from source

[Blargian]

Summary

As part of 2730

• Updates the autogenerate-settings.sh file for already auto-generated core and format settings to use Template format.
• Adds query to auto-generate merge-tree settings (system.merge_tree_settings).
• Adds a readme to make clear how to work with the autogenerated documentation.

Checklist

• Delete items not relevant to your PR
• URL changes should add a redirect to the old URL via https://github.com/ClickHouse/clickhouse-docs/blob/main/docusaurus.config.js
• If adding a new integration page, also add an entry to the integrations list here: https://github.com/ClickHouse/clickhouse-docs/blob/main/docs/en/integrations/index.mdx