Light client roadmap: implement "blsync" tool

[zsfelfoldi]

Status: implemented, needs review + merge
Relevant branches:

• CommitteeChain data structure
  • https://github.com/zsfelfoldi/go-ethereum/tree/committee_chain
  • beacon/light: add CommitteeChain #27766
• blsync tool without finalized head feature
  • https://github.com/zsfelfoldi/go-ethereum/tree/blsync-nofinal4
    • REST API client side implementation
    • request/sync mechanism
    • flags, parameters
    • main logic (retrieve head blocks, call engine API)
• blsync tool with finalized head feature
  • https://github.com/zsfelfoldi/go-ethereum/tree/blsync-final4
    • beacon state API endpoint client side
    • autodetect whether a suitable API is available
    • fetch finalized beacon head and beacon -> EL head hash associations
    • add correct finalized EL head to engine API calls when available

[s1na]

I think this can be closed?