Optimize BeaconState with Lighthouse v5.2.0 Tree-States Upgrade

Lighthouse v5.2.0 reworks BeaconState using a persistent binary merkle tree with structural sharing, cutting memory per state from 500 MB. This enables near-instant access to multiple states, speeding reorgs and reducing copying from O(n) to O(1). The Milhouse library underpins this, optimizing tree mutations despite slower random access O(log n) versus arrays’ O(1). Rebasing de-duplicates trees on load, saving memory.