Merge pull request #44897 from msau42/local-storage-plugin

Automatic merge from submit-queue (batch tested with PRs 46076, 43879, 44897, 46556, 46654)

Local storage plugin

**What this PR does / why we need it**:
Volume plugin implementation for local persistent volumes.  Scheduler predicate will direct already-bound PVCs to the node that the local PV is at.  PVC binding still happens independently.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: 
Part of #43640

**Release note**:

```
Alpha feature: Local volume plugin allows local directories to be created and consumed as a Persistent Volume.  These volumes have node affinity and pods will only be scheduled to the node that the volume is at.
```

pkg/api/helper/helpers.go

@@ -590,6 +590,10 @@ func GetStorageNodeAffinityFromAnnotation(annotations map[string]string) (*api.N
 // Converts NodeAffinity type to Alpha annotation for use in PersistentVolumes
 // TODO: update when storage node affinity graduates to beta
 func StorageNodeAffinityToAlphaAnnotation(annotations map[string]string, affinity *api.NodeAffinity) error {
+	if affinity == nil {
+		return nil
+	}
+
 	json, err := json.Marshal(*affinity)
 	if err != nil {
 		return err