Merge Lighthouse and Reth into Single Binary with Fullhouse

Fullhouse merges Lighthouse and Reth in one binary, replacing HTTP JSON-RPC with direct Engine API calls including forkchoice_updated, new_payload, get_payload, get_blobs_v1/v2. Tested on Hoodi testnet, Fullhouse excels in get_blobs_v2 latency but lags in new_payload and block production. Memory use is similar; CPU load is higher. Run with fullhouse bn --checkpoint-sync-url. Code on GitHub: jimmygchen/lighthouse/lighthouse-reth.