Automatically cleanup provider cache Secret on upgrade.

[anmazzotti]

Detailed Description

On provider version upgrade, the previous cache Secret seems to stay.
These Secrets are normally packed with data, and since rolling back a provider is not a supported operation, there's no reason for the old cache to still exist. I believe it should be deleted.

> kubectl -n capv-system get secrets
NAME                                   TYPE                DATA   AGE
capv-manager-bootstrap-credentials     Opaque              1      2m45s
capv-webhook-service-cert              kubernetes.io/tls   3      4m42s
infrastructure-vsphere-v1.12.0-cache   Opaque              1      4m42s
infrastructure-vsphere-v1.13.0-cache   Opaque              1      2m47s

/kind feature

[k8s-ci-robot]

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