Generates beacon chain Merkle proofs and encodes EigenPod.verifyWithdrawalCredentials().
Returns an array of transactions batched by ~60 validators per tx. Must be executed in order.

Validators are auto-detected from the staker's EigenPod — no validatorPubkeys parameter is needed.

Nonce handling: The nonce is computed at call time. If you prepare multiple transactions before broadcasting, they will share the same nonce and only the first will succeed. Broadcast and confirm each transaction before preparing the next.