refactor: Register types with scheme using pattern from Cluster API (#1124)

**What problem does this PR solve?**:
This pattern removes the dependency on controller-runtime from the API
module. It is recommended by Cluster API.


https://cluster-api.sigs.k8s.io/developer/providers/getting-started/implement-api-types#registering-apis-in-the-scheme

**Which issue(s) this PR fixes**:
Fixes #

**How Has This Been Tested?**:
<!--
Please describe the tests that you ran to verify your changes.
Provide output from the tests and any manual steps needed to replicate
the tests.
-->

**Special notes for your reviewer**:
<!--
Use this to provide any additional information to the reviewers.
This may include:
- Best way to review the PR.
- Where the author wants the most review attention on.
- etc.
-->
Because the api module contains external types that do have a dependency
on controller-runtime, we have to make a similar change to these types
upstream before we can remove our dependency on controller-runtime.

Author: dlipovetsky

api/v1alpha1/clusterconfig_types.go

@@ -330,7 +330,7 @@ type CoreDNS struct {
 
 //nolint:gochecknoinits // Idiomatic to use init functions to register APIs with scheme.
 func init() {
-	SchemeBuilder.Register(
+	objectTypes = append(objectTypes,
 		&AWSClusterConfig{},
 		&DockerClusterConfig{},
 		&NutanixClusterConfig{},

api/v1alpha1/groupversion_info.go

@@ -4,8 +4,9 @@
 package v1alpha1
 
 import (
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	runtime "k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
-	"sigs.k8s.io/controller-runtime/pkg/scheme"
 )
 
 const APIGroup = "caren.nutanix.com"
@@ -14,9 +15,17 @@ var (
 	// GroupVersion is group version used to register these objects.
 	GroupVersion = schema.GroupVersion{Group: APIGroup, Version: "v1alpha1"}
 
-	// SchemeBuilder is used to add go types to the GroupVersionKind scheme.
-	SchemeBuilder = &scheme.Builder{GroupVersion: GroupVersion}
+	// schemeBuilder is used to add go types to the GroupVersionKind scheme.
+	schemeBuilder = runtime.NewSchemeBuilder(addKnownTypes)
 
 	// AddToScheme adds the types in this group-version to the given scheme.
-	AddToScheme = SchemeBuilder.AddToScheme
+	AddToScheme = schemeBuilder.AddToScheme
+
+	objectTypes = []runtime.Object{}
 )
+
+func addKnownTypes(scheme *runtime.Scheme) error {
+	scheme.AddKnownTypes(GroupVersion, objectTypes...)
+	metav1.AddToGroupVersion(scheme, GroupVersion)
+	return nil
+}

api/v1alpha1/nodeconfig_types.go

@@ -166,7 +166,7 @@ type NodeRegistrationOptions struct {
 
 //nolint:gochecknoinits // Idiomatic to use init functions to register APIs with scheme.
 func init() {
-	SchemeBuilder.Register(
+	objectTypes = append(objectTypes,
 		&AWSWorkerNodeConfig{},
 		&DockerWorkerNodeConfig{},
 		&NutanixWorkerNodeConfig{},