Split CRI image service from GRPC handler

Prepares the CRI image service for splitting CRI into multiple plugins.
Also prepares for config migration which will spread across multiple
different plugins.

Signed-off-by: Derek McGowan <derek@mcg.dev>

pkg/cri/server/images/image_pull_test.go

@@ -274,7 +274,7 @@ func TestRegistryEndpoints(t *testing.T) {
 	} {
 		test := test
 		t.Run(test.desc, func(t *testing.T) {
-			c := newTestCRIService()
+			c, _ := newTestCRIService()
 			c.config.Registry.Mirrors = test.mirrors
 			got, err := c.registryEndpoints(test.host)
 			assert.NoError(t, err)
@@ -368,7 +368,7 @@ func TestDefaultScheme(t *testing.T) {
 //	} {
 //		test := test
 //		t.Run(test.desc, func(t *testing.T) {
-//			c := newTestCRIService()
+//			c, _ := newTestCRIService()
 //			c.config.ImageDecryption.KeyModel = test.keyModel
 //			got := len(c.encryptedImagesPullOpts())
 //			assert.Equal(t, test.expectedOpts, got)
@@ -424,7 +424,7 @@ func TestSnapshotterFromPodSandboxConfig(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.desc, func(t *testing.T) {
-			cri := newTestCRIService()
+			cri, _ := newTestCRIService()
 			cri.config.ContainerdConfig.Snapshotter = defaultSnashotter
 			cri.config.ContainerdConfig.Runtimes = make(map[string]criconfig.Runtime)
 			cri.config.ContainerdConfig.Runtimes["exiting-runtime"] = criconfig.Runtime{
@@ -487,7 +487,7 @@ func TestGetRepoDigestAndTag(t *testing.T) {
 
 func TestImageGetLabels(t *testing.T) {
 
-	criService := newTestCRIService()
+	criService, _ := newTestCRIService()
 
 	tests := []struct {
 		name               string