Add defaultAsset attribute to chains in config package.

[chrisli30]

We used to define the defaultAsset for every chain, and I think that’s still required making the config convenient for developers. Let’s add the values back.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.