api/events: split event types from events service

To avoid importing all of grpc when consuming events, the types of
events have been split in to a separate package. This should allow a
reduction in memory usage in cases where a package is consuming events
but not using the gprc service directly.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

events/exchange/exchange_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	eventstypes "github.com/containerd/containerd/api/events"
 	v1 "github.com/containerd/containerd/api/services/events/v1"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/events"
@@ -19,9 +20,9 @@ import (
 func TestExchangeBasic(t *testing.T) {
 	ctx := namespaces.WithNamespace(context.Background(), t.Name())
 	testevents := []events.Event{
-		&v1.ContainerCreate{ID: "asdf"},
-		&v1.ContainerCreate{ID: "qwer"},
-		&v1.ContainerCreate{ID: "zxcv"},
+		&eventstypes.ContainerCreate{ID: "asdf"},
+		&eventstypes.ContainerCreate{ID: "qwer"},
+		&eventstypes.ContainerCreate{ID: "zxcv"},
 	}
 	exchange := NewExchange()
 
@@ -80,7 +81,7 @@ func TestExchangeBasic(t *testing.T) {
 				if err != nil {
 					t.Fatal(err)
 				}
-				received = append(received, ev.(*v1.ContainerCreate))
+				received = append(received, ev.(*eventstypes.ContainerCreate))
 			case err := <-subscriber.errq:
 				if err != nil {
 					t.Fatal(err)
@@ -118,7 +119,7 @@ func TestExchangeValidateTopic(t *testing.T) {
 		},
 	} {
 		t.Run(testcase.input, func(t *testing.T) {
-			event := &v1.ContainerCreate{ID: t.Name()}
+			event := &eventstypes.ContainerCreate{ID: t.Name()}
 			if err := exchange.Publish(ctx, testcase.input, event); errors.Cause(err) != testcase.err {
 				if err == nil {
 					t.Fatalf("expected error %v, received nil", testcase.err)