fix: handle case when tally is equal in common_highest_checkpoint

[shariqnaiyer]

What was wrong?

When comparing checkpoints from peers. We tally peers but in case of a tie, we should choose the checkpoint with the highest slot.

This should fix the late joiner test on Devnet3.

How was it fixed?

let mut highest_tally = 0;
        for (checkpoint, tally) in checkpoint_tally {
            if tally > highest_tally
                || (tally == highest_tally
                    && common_checkpoint
                        .is_some_and(|common_checkpoint| checkpoint.slot > common_checkpoint.slot))
            {
                highest_tally = tally;
                common_checkpoint = Some(checkpoint);
            }
        }

        common_checkpoint

I initially expanded the if statement which looked a little ugly to read and found a clean way to do the loop.

Tuples in Rust are compared left to right so it's equivalent to the above loop.

To-Do

• I have read CONTRIBUTING.md.
• This PR title follows conventional commits.

[KolbyML]

I need to look more into this

[KolbyML]

Looks good

[Kayden-ML]

Looks good 👍