Merge Info UX improvements

[philknows]

UPDATE: Enlarging the scope of the issue to:

• Optimize the merge tracker
• Add merge metrics
• Add merge info logger
  Is your feature request related to a problem? Please describe.

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Reference Lighthouse issue: sigp/lighthouse#3249

This was mentioned in the Eth R&D chats as a beneficial UX opportunity for those running Lodestar awaiting the transition up to the merge.

Currently Teku has this in their logs:
teku | 10:29:18.306 INFO - TTD ETA: 0 days, 4 hours and 22 minutes (8 Jun 2022 - 14:51:48) - Current Total Difficulty: 0x00000000000000000000000000000000000000000000000000ace84463a84fd1

Describe the solution you'd like

It would be good for Lodestar to periodically log a line that shows:

• Difficulty of last block in a non-hex format
• Total difficulty required to hit merge (re-iterates that the TTD settings are correct)
• ETA if we are able to get the hashrate or total avg difficulty of previous X blocks (whatever metric would be best to estimate)

[dapplion]

Sounds good! I support this

[dapplion]

Implementation guidelines for implementer

Create a new TimeSeries with more points (100) to track TTD

lodestar/packages/beacon-node/src/node/notifier.ts

Line 33 in 684c2e3

const timeSeries = new TimeSeries({maxPoints: 10});

ttd should be exposed on a getter on this class

lodestar/packages/beacon-node/src/eth1/eth1MergeBlockTracker.ts

Line 43 in 684c2e3

export class Eth1MergeBlockTracker {

everytime it fetches a block, persist the max TD seen in a variable this.maxTD. Then this variable should be re-used in a counter collect fn