Add graphql forward function

[VGSML]

Add graphql forward function to support forward GraphQL query as is or with transform to original names to a separate service (http source) or by endpoint.
The main goal - run graphql on the separate GraphQL service.

For begin - implement forwarding GraphQL query to the cluster management node and return results from each node, something like this:

original query:

query($var1: Type1!, $var2:Type2){
  core{
    cluster{
      query_nodes{
        node
        query{
          devices(filter:$var1){
            id
            name
            description
            geom
            events(filter:{
              event_time: {
                gt: "2025-04-01T17:25"
                lte: "2025-04-01T17:25"
              }
              type: {
                eq: $var2
              }
            })
          }
        }
      }
    }
  }
}

forwarded query:

query($var1:OriginalType!, $var2: String){
  query_nodes{
    node
    query{
      devices_original_name(filter:$var1){
        id
        name
        description
        geom
        events(filter:{
          event_time: {
            gt: "2025-04-01T17:25"
            lte: "2025-04-01T17:25"
          }
          type: {
            eq: $var2
          }
        })
      }
    }
  }
}

This can be implemented as special SQL UDF - forward_graphql and should be defined a special query type (the same way as function or select), and special plan node, that serialises selection set as query and variables to JSON, and perform http call.