Cardano Updates

## Description
<!--- Describe your changes -->
- Adds a new /pool_invalid_delegators RPC. This fetches any invalid
delegations for a given pool and epoch.
- /pool_delegators now returns valid delegations even if they have 0
balance
- /pool_delegators no longer returns invalid delegations
- /drep_info returns a new `drep_status` field instead of `registered`,
aligned with /pool_info


## Which issue it fixes?
<!--- Link to issue: Closes #issue-number -->

Closes #323

---------

Co-authored-by: RdLrT <[email protected]>

## Description
<!--- Describe your changes -->
Fixes this issue

```
2026-01-20_22:20:01 Running next epoch nonce calculation...
/opt/cardano/cnode/scripts/cron-scripts/populate-next-epoch-nonce.sh: line 30: TYPE
1183: syntax error in expression (error token is "1183")
/opt/cardano/cnode/scripts/cron-scripts/populate-next-epoch-nonce.sh: line 32: [[: TYPE
76744: syntax error in expression (error token is "76744")
2026-01-20_22:20:01 Job done!
```

---------

Co-authored-by: RdLrT <[email protected]>

## Description
<!--- Describe your changes -->

Fixes retiring epoch not updating after initial insert.