How exactly does Layerzero Protocol send the txs from one chain to another, Integration used one endpoint to send the tx, like for eg, the Omni NFT standard... There is a function called debitFrom, this takes data from dest chain and send to endpoint whilr burning the nft...and a credit to function that takes the data from for minting a new nft on the destination chain ... What I wanna understand is how exactly do they achieve that seamless cross-chain data transfers, Do they use external servers and all, or is somehow cross Blockchain data transfers are possible without any external data relayers