Integrate 'statuses' Query Parameter Support in getValidators Function

[boulder225]

🎯 Problem to be solved

getValidators function does not fully align with the specs, as it only reads ids from the query parameters, while the spec mentions both ids and statuses. The go-eth2-client library, which we depend on, does not support statuses as a query parameter. This discrepancy could limit our validator API, potentially missing out on filtering.

🛠️ Proposed solution

• [ ] Support go-eth2-client project by proposing a PR supporting statuses.
• [ ] For now, have TODOs in our codebase to integrate statuses parameter support once it becomes available in the go-eth2-client library.

[pinebit]

Confirmed with attestant: once this API gets stable and supported by various clients, we can take it into development.

[pinebit]

This ticket is ready to go, but it requires the new version of the go-eth2-client, which is to be integrated under #2936

[pinebit]

We probably don't need this.