Deprecate client/selector (#1767)

* client/{grpc,rpc}: depricate selector (wip)

* {client,cmd}: remove client/selector

* deprecate client/selector

* router/static: fix lookup

* config/cmd: add support for legacy static selector flag

* config/cmd: add support for legacy dns selector flag

client/grpc/grpc_test.go

@@ -6,10 +6,10 @@ import (
 	"testing"
 
 	"github.com/micro/go-micro/v2/client"
-	"github.com/micro/go-micro/v2/client/selector"
 	"github.com/micro/go-micro/v2/errors"
 	"github.com/micro/go-micro/v2/registry"
 	"github.com/micro/go-micro/v2/registry/memory"
+	"github.com/micro/go-micro/v2/router"
 	pgrpc "google.golang.org/grpc"
 	pb "google.golang.org/grpc/examples/helloworld/helloworld"
 )
@@ -56,16 +56,11 @@ func TestGRPCClient(t *testing.T) {
 		},
 	})
 
-	// create selector
-	se := selector.NewSelector(
-		selector.Registry(r),
-	)
+	// create router
+	rtr := router.NewRouter(router.Registry(r))
 
 	// create client
-	c := NewClient(
-		client.Registry(r),
-		client.Selector(se),
-	)
+	c := NewClient(client.Router(rtr))
 
 	testMethods := []string{
 		"/helloworld.Greeter/SayHello",