fix: Discover default storage class when none specified

[jonathan-innis]

Fixes aws/karpenter-provider-aws#3647

Description

Previously, when the following volumeClaimTemplate was used for Deployments, we would not discover the storageClassName that is being used as the default and fail to find the driver associated with a volume

volumes:
- name: scratch-volume
  ephemeral:
      volumeClaimTemplate:
         spec:
           accessModes: [ "ReadWriteOnce" ]
           resources:
             requests:
               storage: 3Gi

This meant that Karpenter and the kube-scheduler would disagree. Karpenter would think that more pods could schedule on the node and the kube-scheduler would reject this due to the volume limits on the node. This change fixes this discovery by finding the default storage class (if one is specified) and using that if no storageClassName is specified

How was this change tested?

• make presubmit
• Manual Testing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[coveralls]

Pull Request Test Coverage Report for Build 4696862521

• 21 of 25 (84.0%) changed or added relevant lines in 1 file are covered.
• 19 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.2%) to 81.423%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/scheduling/volumeusage.go	21	25	84.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/controllers/state/cluster.go	6	84.47%
pkg/controllers/deprovisioning/controller.go	13	79.51%

Totals
Change from base Build 4692105904:	0.2%
Covered Lines:	6750
Relevant Lines:	8290

---

💛 - Coveralls

[tzneal]

lgtm