Feature request: Add support for Oracle Container Registry automatic authentication

[matheuscscp]

I'd like to authenticate automatically to Oracle Container Registry using something similar to:

https://docs.oracle.com/en-us/iaas/Content/ContEng/Tasks/contenggrantingworkloadaccesstoresources.htm

[stefanprodan]

To implement auth for Oracle, we'll need some org to sponsor the Flux project so we can run e2e tests and provision clusters and registry repos in Oracle Cloud. The workload id code to access container registries is here https://github.com/fluxcd/pkg/tree/main/oci/auth. The oci/auth package is used by the Flux CLI, source-controller and image-reflector-controller, if we are going to support Oracle IAM, we'll need to integrate it with all Flux components.