Add support for OKE Workload Identity

[hyder]

OKE has a feature called OKE Workload Identity. This makes it considerably easier and more secure to configure pods to authenticate and access OCI services e.g. https://medium.com/oracledevs/kubernetes-monitoring-with-verrazzano-prometheus-thanos-and-workload-identity-on-oracle-cloud-ff35fafb547a.

For the ora-operator, it would be most helpful if OKE Workload Identity can be added so that the ora-operator can provision new databases or bind to existing ones and create the wallets without the need to set up the OCI private key nor instance principal.

[hyder]

Resolved in #98.

In future, please ensure community contributions (#91) are reviewed and merged.