Consistent return type signature for @fuels/react hooks

[petertonysmith94]

Summary

For context, the @FuelLabs/sdk-ts team had a discussion here around the return type of useWallet, which is inconsistent with the rest of the hooks in @fuels/react (examples below).

• Provide consistent return types across all hooks, for an easier typed experience for consumers.

useWallet

declare const useWallet: (address?: string | null) => {
    // Omitted irrelevant return variables
    wallet: fuels.Account | null | undefined;
};

getBalance

declare const useBalance: () => {
    // Omitted irrelevant return variables
    balance: fuels.BN | null;
};