Add controller stubs for API Gateway (#15837)

* update initial stub implementation

* move files, clean up mutex references

* Remove embed, use idiomatic names for constructors

* Remove stray file introduced in merge

Co-authored-by: Nathan Coleman <nathan.coleman@hashicorp.com>

agent/consul/gateways/controller_gateways.go

@@ -2,13 +2,11 @@ package gateways
 
 import (
 	"context"
-
-	"github.com/hashicorp/go-hclog"
-
 	"github.com/hashicorp/consul/agent/consul/controller"
 	"github.com/hashicorp/consul/agent/consul/fsm"
 	"github.com/hashicorp/consul/agent/consul/state"
 	"github.com/hashicorp/consul/agent/consul/stream"
+	"github.com/hashicorp/go-hclog"
 )
 
 type apiGatewayReconciler struct {

agent/consul/gateways/controller_routes.go

@@ -2,13 +2,11 @@ package gateways
 
 import (
 	"context"
-
-	"github.com/hashicorp/go-hclog"
-
 	"github.com/hashicorp/consul/agent/consul/controller"
 	"github.com/hashicorp/consul/agent/consul/fsm"
 	"github.com/hashicorp/consul/agent/consul/state"
 	"github.com/hashicorp/consul/agent/consul/stream"
+	"github.com/hashicorp/go-hclog"
 )
 
 type tcpRouteReconciler struct {