Metrics to add tracker

## Ready to execute

- https://github.com/ChainSafe/lodestar/issues/2483
- https://github.com/ChainSafe/lodestar/issues/2984
- https://github.com/ChainSafe/lodestar/issues/3033
- https://github.com/ChainSafe/lodestar/issues/3112
- https://github.com/ChainSafe/lodestar/issues/3115
- https://github.com/ChainSafe/lodestar/issues/3205
- https://github.com/ChainSafe/lodestar/issues/3413
- https://github.com/ChainSafe/lodestar/issues/3680
- https://github.com/ChainSafe/lodestar/issues/3946
- https://github.com/ChainSafe/lodestar/pull/4122 ReqResp request times
- https://github.com/ChainSafe/lodestar/pull/4123 Reorg depth histogram
- https://github.com/ChainSafe/lodestar/pull/4123 Distance to parent block histogram
- https://github.com/ChainSafe/lodestar/pull/4124 Histogram of balance increase for block proposer
- https://github.com/ChainSafe/lodestar/pull/4125 Total signatures aggregated (optional histogram for time spent aggregating)
- https://github.com/ChainSafe/lodestar/pull/4127 JSON RPC client metrics
- From Lighthouse: https://github.com/ChainSafe/lodestar/issues/4273
- From Lighthouse: https://github.com/ChainSafe/lodestar/issues/4274
- From Lighthouse: https://github.com/ChainSafe/lodestar/issues/2558
- From Lighthouse: https://github.com/ChainSafe/lodestar/issues/2984
- From Lighthouse: https://github.com/ChainSafe/lodestar/issues/2473

## Metric ideas

### Misc

Once properly defined, convert to issue or pull request and move above to "**Ready to execute**"

- Improve state.clone() metrics, what we really care about is before doing state-transitions if the state has cache or not.
- Add more sync metrics to measure efficiency: # blocks downloaded to process # of blocks. To count duplicated downloads indirectly.
- Discv5 ping times
- Gossipsub received blocks
- Blocks in last epoch, to compute percent of orphaned
- More HTTP metrics?

### From Lighthouse

Reviewed this file and select interesting metrics to add
https://github.com/sigp/lighthouse/blob/stable/beacon_node/beacon_chain/src/metrics.rs

**Block Delay Metrics**

- [x] `beacon_block_imported_slot_start_delay_time`: Duration between the start of the blocks slot and the current time when it was imported.
- [x] `beacon_block_head_slot_start_delay_time`: Duration between the start of the blocks slot and the current time when it was as head.
- [ ] `beacon_block_head_slot_start_delay_exceeded_total`: Triggered when the duration between the start of the blocks slot and the current time will result in failed attestations. https://github.com/ChainSafe/lodestar/pull/5559

**Persisting BeaconChain components to disk**

- [ ] `beacon_persist_head`: Time taken to persist the canonical head
- [ ] `beacon_persist_op_pool`: Time taken to persist the operations pool - Does Lighthouse keep all ops in memory?
- [ ] `beacon_persist_eth1_cache`: Time taken to persist the eth1 caches

**Chain Head**

- [x] `beacon_update_head_seconds`: Time taken to update the canonical head - Review what does it refer too

Start by reviewing the linked Lodestar issues and pull requests, then compare the metric ideas with Lighthouse's beacon_node/beacon_chain/src/metrics.rs. The tracker is done when a metric is properly defined, converted into a concrete issue or pull request, and moved to the Ready to execute section.

Written by the indexing model from the issue text.