chore: use `fuel-core` `0.31.0`

[hal3e]

I had to change the logic of get_contract_balances as we were requesting 9999 coins which resulted in a to complex graph-ql query. Now we request in batches of 512. Thanks @xgreenx for you feedback.

Checklist

• [x] I have added necessary labels.
• [x] I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• [x] I have requested a review from the relevant team or maintainers.