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/api_metrics.md

@@ -0,0 +1,85 @@
+# Prometheus Metrics
+
+Lighthouse provides an extensive suite of metrics and monitoring in the
+[Prometheus](https://prometheus.io/docs/introduction/overview/) export format
+via a HTTP server built into Lighthouse.
+
+These metrics are generally consumed by a Prometheus server and displayed via a
+Grafana dashboard. These components are available in a docker-compose format at
+[sigp/lighthouse-metrics](https://github.com/sigp/lighthouse-metrics).
+
+## Beacon Node Metrics
+
+By default, these metrics are disabled but can be enabled with the `--metrics`
+flag. Use the `--metrics-address`, `--metrics-port` and
+`--metrics-allow-origin` flags to customize the metrics server.
+
+### Example
+
+Start a beacon node with the metrics server enabled:
+
+```bash
+lighthouse bn --metrics
+```
+
+Check to ensure that the metrics are available on the default port:
+
+```bash
+curl localhost:5054/metrics
+```
+
+## Validator Client Metrics
+
+By default, these metrics are disabled but can be enabled with the `--metrics`
+flag. Use the `--metrics-address`, `--metrics-port` and
+`--metrics-allow-origin` flags to customize the metrics server.
+
+### Example
+
+Start a validator client with the metrics server enabled:
+
+```bash
+lighthouse vc --metrics
+```
+
+Check to ensure that the metrics are available on the default port:
+
+```bash
+curl localhost:5064/metrics
+```
+
+## Remote Monitoring
+
+Lighthouse has the ability to send a subset of metrics to a remote server for collection. Presently
+the main server offering remote monitoring is beaconcha.in. Instructions for setting this up
+can be found in beaconcha.in's docs:
+
+- <https://kb.beaconcha.in/beaconcha.in-explorer/mobile-app-less-than-greater-than-beacon-node>
+
+The Lighthouse flag for setting the monitoring URL is `--monitoring-endpoint`.
+
+When sending metrics to a remote server you should be conscious of security:
+
+- Only use a monitoring service that you trust: you are sending detailed information about
+  your validators and beacon node to this service which could be used to track you.
+- Always use an HTTPS URL to prevent the traffic being intercepted in transit.
+
+The specification for the monitoring endpoint can be found here:
+
+- <https://github.com/gobitfly/eth2-client-metrics>
+
+_Note: the similarly named [Validator Monitor](./validator_monitoring.md) feature is entirely
+independent of remote metric monitoring_.
+
+### Update Period
+
+You can adjust the frequency at which Lighthouse sends metrics to the remote server using the
+`--monitoring-endpoint-period` flag. It takes an integer value in seconds, defaulting to 60
+seconds.
+
+```bash
+lighthouse bn --monitoring-endpoint-period 60 --monitoring-endpoint "https://url"
+```
+
+Increasing the monitoring period between can be useful if you are running into rate limits when
+posting large amounts of data for multiple nodes.