Validators Sync

[kmolinski-reef]

Validator Manager is a separate app which holds and updates models instances based on the Validators config.
The Validators config is supposed to list external validators with their default and child hotkeys by the subnet.

• The models are accessible through the /validator-admin admin panel
• The celery job is handling the constant sync with the validators config
• The models, most especially ExternalHotkey are going to be extended by the upcoming PR's when the chain sync function will be provided.

The core app is extended with same functionality and more:

• The validators auto-sync enabled/disabled in the admin panel
• The manual validators sync
• Delegate stake form in the subnets panel