[Feature]: Relax finality check on Arbitrum

[wwestgarth]

Feature Overview

In order to make deposits on Arbitrum very quick and to avoid special complex code in FE
We will relax the finality check on Arbitrum simply check for existence on the latest block

There was a discussion about it on slack here:
https://vegaprotocol.slack.com/archives/CAHA5EX0F/p1718882784583639

The summary is that currently core waits for a Arbitrum block to be marked as safe which means the sequence has submitted its rollup of sequenced events to Ethereum. What was noticed is that this does not mean thatany sort of consensus was reached on Arbitrum. The roll-up only commits the sequence of transaction onto a blockchain and the Arbitrum nodes have 1 week to decided that the result of every other validator matches theres.

For Vega,we already have a consensus check on EVM chain events, namely, that for a given chain-event 2/3's of the voting power must agree that they saw that chain-event happen. If each validator has themselves chosen a trusted Arbitrum node then this is sufficient that the chain-event can be trusted.

I believe this change is a one liner to change here the FinalityStateSafe -> FinalityStateLatest:

n.secondaryEthConfirmations = ethclient.NewEthereumConfirmations(n.conf.Ethereum, n.secondaryEthClient, nil, ethclient.FinalityStateSafe)

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