feat: add ephemery network

[atkinsonholly]

Description

Add ephemery as a network option, requiring additions to packages/cli, packages/config and packages/prover.

This PR addresses the first, second and third tasks of issue#6050, relating to:

• Add ephemery flag
• Use backup download URL (ephemery.dev)
• Use flag to override with custom path to a genesis.ssz file provided by user

Steps to test or reproduce

Checkout the branch:

git checkout atkinsonholly/ephemery-config

To run the ephemery network using the genesis.ssz download available at https://ephemery.dev/latest/genesis.ssz, run:

lodestar beacon --ephemery

which should show

warn: Initializing from a stale checkpoint state vulnerable to long range attacks
warn: Checkpoint sync recommended

To run the ephemery network using the checkpoint sync flag (recommended), run:

lodestar beacon --network ephemery --checkpointSyncUrl https://checkpointz.bordel.wtf/

which should result in

info: Initializing beacon from a valid checkpoint state

To run the ephemery network with a local genesis state file, run:

lodestar beacon ephemery --genesisStateFile path/to/genesis.ssz

[CLAassistant]

All committers have signed the CLA.

[nflaig]

Looks pretty good overall, thanks for the updates.

I was able to verify that Lodestar can join the network by running

./lodestar beacon --network ephemery --execution.engineMock --eth1 false

and seems to be able to follow the chain, peer count is a bit low but might be due to low network participation

info: Synced - slot: 34269 - head: 0x9db9…87f6 - exec-block: syncing(31423 0x7ac5…) - finalized: 0x7339…cd93:1068 - peers: 6
info: Synced - slot: 34270 - head: 0x6b41…442e - exec-block: syncing(31424 0x98b2…) - finalized: 0x7339…cd93:1068 - peers: 6
info: Synced - slot: 34271 - head: 0xbff4…9c82 - exec-block: syncing(31425 0x0be5…) - finalized: 0x7339…cd93:1068 - peers: 6
info: Synced - slot: 34272 - head: 0x909f…8388 - exec-block: syncing(31426 0x88f6…) - finalized: 0x2ccb…1d8d:1069 - peers: 6

This should cover the basic support mentioned in EIP 6916 rationale

[nflaig]

From the spec

It's important to note that genesis_validators_root is normally predefined in the client but in this case it's not known in advance which can potentially break certain architectures. For example light clients which are relying on hardcoded genesis_validators_root won't work.

Not sure how to resolve this issue, @g11tech maybe you have some thoughts on this.

[nflaig]

lgtm, thanks for the cleanup and adding references

[wemeetagain]

🎉 This PR is included in v1.12.0 🎉