Some updates to Lighthouse book (#6995)

* #6447


  - Move some deprecated pages to a new section under `Archived`

- Remove fallback log in mev as the log will not be present after VC using `/eth/v3/validator/blocks` endpoint by default
- Add warning against using Btrfs file system (thank you @ChosunOne for the report)
- Add data shared by @mcdee  on tree states API queries time
- Rename partial withdrawals to validator sweep to differentiate it from the upcoming execution layer partial withdrawals
- Update NAT API response
- Update docs on IPv6

- Rename .md files to follow a standard prefix section name, e.g., installation_*.md, advanced_*.md
- Standardise .md files using underscore `_` instead of hyphen `-` to be consistent with other files naming conventions.

book/src/ui.md

@@ -0,0 +1,33 @@
+# Lighthouse UI (Siren)
+
+_Documentation for Siren users and developers._
+
+[![Chat Badge]][Chat Link]
+
+[Chat Badge]: https://img.shields.io/badge/chat-discord-%237289da
+[Chat Link]: https://discord.gg/cyAszAh
+
+![ui-overview](./imgs/ui.png)
+
+Siren is a user interface built for Lighthouse that connects to a Lighthouse Beacon Node and
+a Lighthouse Validator Client to monitor performance and display key validator
+metrics.
+
+The UI is currently in active development. It resides in the
+[Siren](https://github.com/sigp/siren) repository.
+
+## Topics
+
+See the following Siren specific topics for more context-specific
+information:
+
+- [Configuration Guide](./ui_configuration.md) - Explanation of how to setup
+ and configure Siren.
+- [Authentication Guide](./ui_authentication.md) - Explanation of how Siren authentication works and protects validator actions.
+- [Usage](./ui_usage.md) - Details various Siren components.
+- [FAQs](./ui_faqs.md) - Frequently Asked Questions.
+
+## Contributing
+
+If you find an issue or bug or would otherwise like to help out with the
+development of the Siren project, please submit issues and PRs to the [Siren](https://github.com/sigp/siren) repository.