Add admin whitelist management to contracts missing the feature

Several contracts lack built-in admin whitelist management (add/remove admin) and currently require a migration to update the admin list. The affected contracts are:

- Hydro (auctions)
- Inflow Skip adapter
- Inflow IBC adapter
- Inflow Mars adapter
- Proxy
- User registry

Hydro and the Inflow adapters are the priority: the new DAOs need to be added as admins, and we want to manage the admin list going forward without migrations.

Since all adapters will share this feature, the proposal is to implement add/remove admin within `StandardAction`, so any newly developed adapter inherits this structure by default. As part of this change, the CCTP adapter will be migrated from `CustomAction` to `StandardAction`.

@p-offtermatt can you confirm whether Proxy and User registry also need this?