Expose the transaction service URL in the ChainInfo

[schmanu]

Feature Request

In order to support all Safe networks some Safe Apps require access to the transaction service on all chains.

Currently in order to do this, safe apps need to fetch the chain configs from the config service in order to find the transaction service URLs for every supported chain.

It would be great to include this information in the ChainInfo returned by sdk.safe.getChainInfo() result.

This would also make Safe Apps compatible with custom forked versions of Safe Wallet that third parties setup for their own chains where they run the full infra stack themselves.

Context

bh2smith/safe-airdrop#628