Allow Relay to be fetched using the GraphQL client API

[petruki]

Is your feature request related to a problem? Please describe.
Switcher Relay are not exposed in our GraphQL APIs. Integration such as Switcher GitOps may use this data to manage Switchers that are managed by Relay.

Describe the solution you'd like
Add Relay type to Config type for the GraphQL API

relay {
    relay_type
    relay_method
    relay_endpoint
    description
    activated
    statusByEnv {
        env
        value
    }
}