Add natively staked assets in the Safe balances

[hectorgomezv]

Description

On Native Staking, the user does not get any asset in return. So the Safe{Wallet} interface does not show any data about the natively staked assets, and their fiat values are also missing from the total balance.

The current flow in the CGW is to check the wallet assets via the Safe Transaction Service API, so it would be necessary to include the staking provider API in the process somehow. As this shouldn't be done for each balance request, ideally an indicator of whether the wallet has staked assets would be needed, and (TBD) this data should be stored in the CGW.

Requirements

• Include the natively staked ETH in the CGW balances responses.

[iamacook]

Having briefly looked into this, we can get the overall balance from the widget endpoint (checking that it's dedicated staking): https://safe.widget.kiln.fi/api/stakes?wallet={{safeAddress}}