[SCOUTCLOUD] Stats, check health, more info in API

[sevenzing]

• add promo feature
• add unhealthy deployment status
• add supervisor job that handles health of instances
• add register api-key endpoint
• update k8s-dev default sub domain to cloud
• add new env variables (env docs)
• add custom stats_enabled env that checks indexing status of blockscout
• add context for generating config that allows some kind of "dependency" between variables, for example stats_enabled depends on instance_url
• update swagger: add field_behavior for required fields