migrate autopilot implementation to raft-autopilot (#14441)

Nomad's original autopilot was importing from a private package in Consul. It
has been moved out to a shared library. Switch Nomad to use this library so that
we can eliminate the import of Consul, which is necessary to build Nomad ENT
with the current version of the Consul SDK. This also will let us pick up
autopilot improvements shared with Consul more easily.

command/agent/operator_endpoint.go

@@ -2,21 +2,20 @@ package agent
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"net"
 	"net/http"
-	"strings"
-
-	"fmt"
 	"strconv"
+	"strings"
 	"time"
 
-	"github.com/hashicorp/consul/agent/consul/autopilot"
 	"github.com/hashicorp/go-msgpack/codec"
+	"github.com/hashicorp/raft"
+
 	"github.com/hashicorp/nomad/api"
 	cstructs "github.com/hashicorp/nomad/client/structs"
 	"github.com/hashicorp/nomad/nomad/structs"
-	"github.com/hashicorp/raft"
 )
 
 // OperatorRequest is used route operator/raft API requests to the implementing
@@ -184,7 +183,7 @@ func (s *HTTPServer) OperatorServerHealth(resp http.ResponseWriter, req *http.Re
 		return nil, nil
 	}
 
-	var reply autopilot.OperatorHealthReply
+	var reply structs.OperatorHealthReply
 	if err := s.agent.RPC("Operator.ServerHealth", &args, &reply); err != nil {
 		return nil, err
 	}